diff --git a/senpy/api.py b/senpy/api.py
index 3b2f605..ee35dad 100644
--- a/senpy/api.py
+++ b/senpy/api.py
@@ -187,22 +187,108 @@ def parse_params(indict, *specs):
     return outdict
 
 
-def parse_extra_params(request, plugins=None):
-    plugins = plugins or []
-    params = request.parameters.copy()
-    for plugin in plugins:
-        if plugin:
-            extra_params = parse_params(params, plugin.get('extra_params', {}))
-            for k, v in extra_params.items():
-                if k not in BUILTIN_PARAMS:
-                    if k in params:  # Set by another plugin
-                        del params[k]
-                    else:
-                        params[k] = v
-                params['{}.{}'.format(plugin.name, k)] = v
+def get_all_params(plugins, *specs):
+    '''Return a list of parameters for a given set of specifications and plugins.'''
+    dic = {}
+    for s in specs:
+        dic.update(s)
+    dic.update(get_extra_params(plugins))
+    return dic
+
+
+def get_extra_params(plugins):
+    '''Get a list of possible parameters given a list of plugins'''
+    params = {}
+    extra_params = {}
+    for i, plugin in enumerate(plugins):
+        this_params = plugin.get('extra_params', {})
+        for k, v in this_params.items():
+            if k not in extra_params:
+                extra_params[k] = []
+            extra_params[k].append(v)
+            params['{}.{}'.format(plugin.name, k)] = v
+            params['{}.{}'.format(i, k)] = v
+    for k, v in extra_params.items():  # Resolve conflicts
+        if len(v) == 1:  # Add the extra options that do not collide
+            params[k] = v[0]
+        else:
+            required = False
+            aliases = None
+            options = None
+            default = None
+            nodefault = False  # Set when defaults are not compatible
+
+            for opt in v:
+                required = required or opt.get('required', False)
+                newaliases = set(opt.get('aliases', []))
+                if aliases is None:
+                    aliases = newaliases
+                else:
+                    aliases = aliases & newaliases
+                if 'options' in opt:
+                    newoptions = set(opt['options'])
+                    options = newoptions if options is None else options & newoptions
+                if 'default' in opt:
+                    newdefault = opt['default']
+                    if newdefault:
+                        if default is None and not nodefault:
+                            default = newdefault
+                        elif newdefault != default:
+                            nodefault = True
+                            default = None
+            # Check for incompatibilities
+            if options != set():
+                params[k] = {
+                    'default': default,
+                    'aliases': list(aliases),
+                    'required': required,
+                    'options': list(options)
+                }
     return params
 
 
+def parse_extra_params(params, plugins):
+    '''
+    Parse the given parameters individually for each plugin, and get a list of the parameters that
+    belong to each of the plugins. Each item can then be used in the plugin.analyse_entries method.
+    '''
+    extra_params = []
+    for i, plugin in enumerate(plugins):
+        this_params = filter_params(params, plugin, i)
+        parsed = parse_params(this_params, plugin.get('extra_params', {}))
+        extra_params.append(parsed)
+    return extra_params
+
+
+def filter_params(params, plugin, ith=-1):
+    '''
+    Get the values within params that apply to a plugin.
+    More specific names override more general names, in this order:
+
+    <index_order>.parameter > <plugin.name>.parameter > parameter
+
+
+    Example:
+
+    >>> filter_params({'0.hello': True, 'hello': False}, Plugin(), 0)
+    { '0.hello': True, 'hello': True}
+
+    '''
+    thisparams = {}
+    if ith >= 0:
+        ith = '{}.'.format(ith)
+    else:
+        ith = ""
+    for k, v in params.items():
+        if ith and k.startswith(str(ith)):
+            thisparams[k[len(ith):]] = v
+        elif k.startswith(plugin.name):
+            thisparams[k[len(plugin.name) + 1:]] = v
+        elif k not in thisparams:
+            thisparams[k] = v
+    return thisparams
+
+
 def parse_call(params):
     '''Return a results object based on the parameters used in a call/request.
     '''
diff --git a/senpy/blueprints.py b/senpy/blueprints.py
index f1cf538..0bc6e40 100644
--- a/senpy/blueprints.py
+++ b/senpy/blueprints.py
@@ -188,15 +188,20 @@ def basic_api(f):
 @api_blueprint.route('/<path:plugin>', methods=['POST', 'GET'])
 @basic_api
 def api_root(plugin):
+    if plugin:
+        if 'algorithm' in request.parameters:
+            raise Error('You cannot specify the algorithm with a parameter and a URL variable.'
+                        ' Please, remove one of them')
+        plugin = plugin.replace('+', '/')
+        request.parameters['algorithm'] = tuple(plugin.split('/'))
+
     if request.parameters['help']:
-        dic = dict(api.API_PARAMS, **api.NIF_PARAMS)
-        response = Help(valid_parameters=dic)
+        sp = current_app.senpy
+        plugins = sp._get_plugins(request)
+        allparameters = api.get_all_params(plugins, api.WEB_PARAMS, api.API_PARAMS, api.NIF_PARAMS)
+        response = Help(valid_parameters=allparameters)
         return response
     req = api.parse_call(request.parameters)
-    if plugin:
-        plugin = plugin.replace('+', '/')
-        plugin = plugin.split('/')
-        req.parameters['algorithm'] = tuple(plugin)
     results = current_app.senpy.analyse(req)
     results.analysis = set(i.id for i in results.analysis)
     return results
diff --git a/senpy/extensions.py b/senpy/extensions.py
index 428186d..054bded 100644
--- a/senpy/extensions.py
+++ b/senpy/extensions.py
@@ -144,7 +144,7 @@ class Senpy(object):
 
         return plugins
 
-    def _process(self, req, pending, done=None):
+    def _process(self, req, parameters, pending, done=None):
         """
         Recursively process the entries with the first plugin in the list, and pass the results
         to the rest of the plugins.
@@ -154,10 +154,11 @@ class Senpy(object):
             return req
 
         plugin = pending[0]
+        req.parameters = parameters[0]
         results = plugin.process(req, conversions_applied=done)
         if plugin not in results.analysis:
             results.analysis.append(plugin)
-        return self._process(results, pending[1:], done)
+        return self._process(results, parameters[1:], pending[1:], done)
 
     def install_deps(self):
         plugins.install_deps(*self.plugins())
@@ -168,10 +169,11 @@ class Senpy(object):
         It takes a processed request, provided by the user, as returned
         by api.parse_call().
         """
+
         logger.debug("analysing request: {}".format(request))
         plugins = self._get_plugins(request)
-        request.parameters = api.parse_extra_params(request, plugins)
-        results = self._process(request, plugins)
+        parameters = api.parse_extra_params(request.parameters, plugins)
+        results = self._process(request, parameters, plugins)
         logger.debug("Got analysis result: {}".format(results))
         results = self.postprocess(results)
         logger.debug("Returning post-processed result: {}".format(results))
diff --git a/senpy/plugins/misc/split_plugin.py b/senpy/plugins/misc/split_plugin.py
index 4c11f3a..d54a6fb 100644
--- a/senpy/plugins/misc/split_plugin.py
+++ b/senpy/plugins/misc/split_plugin.py
@@ -9,7 +9,7 @@ class Split(AnalysisPlugin):
     '''description: A sample plugin that chunks input text'''
 
     author = ["@militarpancho", '@balkian']
-    version = '0.2'
+    version = '0.3'
     url = "https://github.com/gsi-upm/senpy"
 
     extra_params = {
@@ -33,12 +33,15 @@ class Split(AnalysisPlugin):
         if chunker_type == "paragraph":
             tokenizer = LineTokenizer()
         chars = list(tokenizer.span_tokenize(original_text))
-        for i, chunk in enumerate(tokenizer.tokenize(original_text)):
-            print(chunk)
+        if len(chars) == 1:
+            # This sentence was already split
+            return
+        for i, chunk in enumerate(chars):
+            start, end = chunk
             e = Entry()
-            e['nif:isString'] = chunk
+            e['nif:isString'] = original_text[start:end]
             if entry.id:
-                e.id = entry.id + "#char={},{}".format(chars[i][0], chars[i][1])
+                e.id = entry.id + "#char={},{}".format(start, end)
             yield e
 
     test_cases = [
diff --git a/tests/test_api.py b/tests/test_api.py
index 80e16bc..6b8f64f 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -3,8 +3,9 @@ import logging
 logger = logging.getLogger(__name__)
 
 from unittest import TestCase
-from senpy.api import parse_params, API_PARAMS, NIF_PARAMS, WEB_PARAMS
-from senpy.models import Error
+from senpy.api import (boolean, parse_params, get_extra_params, parse_extra_params,
+                       API_PARAMS, NIF_PARAMS, WEB_PARAMS)
+from senpy.models import Error, Plugin
 
 
 class APITest(TestCase):
@@ -89,3 +90,157 @@ class APITest(TestCase):
         assert "Dummy" in p['algorithm']
         assert 'input' in p
         assert p['input'] == 'Aloha my friend'
+
+    def test_parse_extra_params(self):
+        '''The API should parse user parameters and return them in a format that plugins can use'''
+        plugins = [
+            Plugin({
+                'name': 'plugin1',
+                'extra_params': {
+                    # Incompatible parameter
+                    'param0': {
+                        'aliases': ['p1', 'parameter1'],
+                        'options': ['option1', 'option2'],
+                        'default': 'option1',
+                        'required': True
+                    },
+                    'param1': {
+                        'aliases': ['p1', 'parameter1'],
+                        'options': ['en', 'es'],
+
+                        'default': 'en',
+                        'required': False
+                    },
+                    'param2': {
+                        'aliases': ['p2', 'parameter2'],
+                        'required': False,
+                        'options': ['value2_1', 'value2_2', 'value3_3']
+                    }
+                }
+            }), Plugin({
+                'name': 'plugin2',
+                'extra_params': {
+                    'param0': {
+                        'aliases': ['parameter1'],
+                        'options': ['new option', 'new option2'],
+                        'default': 'new option',
+                        'required': False
+                    },
+                    'param1': {
+                        'aliases': ['myparam1', 'p1'],
+                        'options': ['en', 'de', 'auto'],
+                        'default': 'de',
+                        'required': True
+                    },
+                    'param3': {
+                        'aliases': ['p3', 'parameter3'],
+                        'options': boolean,
+                        'default': True
+                    }
+                }
+            })
+        ]
+        call = {
+            'param1': 'en',
+            '0.param0': 'option1',
+            '0.param1': 'en',
+            'param2': 'value2_1',
+            'param0': 'new option',
+            '1.param1': 'de',
+            'param3': False,
+        }
+        expected = [
+            {
+                'param0': 'option1',
+                'param1': 'en',
+                'param2': 'value2_1',
+            }, {
+                'param0': 'new option',
+                'param1': 'de',
+                'param3': False,
+            }
+
+        ]
+        p = parse_extra_params(call, plugins)
+        for i, arg in enumerate(expected):
+            for k, v in arg.items():
+                assert p[i][k] == v
+
+    def test_get_extra_params(self):
+        '''The API should return the list of valid parameters for a set of plugins'''
+        plugins = [
+            Plugin({
+                'name': 'plugin1',
+                'extra_params': {
+                    # Incompatible parameter
+                    'param0': {
+                        'aliases': ['p1', 'parameter1'],
+                        'options': ['option1', 'option2'],
+                        'default': 'option1',
+                        'required': True
+                    },
+                    'param1': {
+                        'aliases': ['p1', 'parameter1'],
+                        'options': ['en', 'es'],
+                        'default': 'en',
+                        'required': False
+                    },
+                    'param2': {
+                        'aliases': ['p2', 'parameter2'],
+                        'required': False,
+                        'options': ['value2_1', 'value2_2', 'value3_3']
+                    }
+                }
+            }), Plugin({
+                'name': 'plugin2',
+                'extra_params': {
+                    'param0': {
+                        'aliases': ['parameter1'],
+                        'options': ['new option', 'new option2'],
+                        'default': 'new option',
+                        'required': False
+                    },
+                    'param1': {
+                        'aliases': ['myparam1', 'p1'],
+                        'options': ['en', 'de', 'auto'],
+                        'default': 'de',
+                        'required': True
+                    },
+                    'param3': {
+                        'aliases': ['p3', 'parameter3'],
+                        'options': boolean,
+                        'default': True
+                    }
+                }
+            })
+        ]
+
+        expected = {
+            # Each plugin's parameters
+            '0.param0': plugins[0]['extra_params']['param0'],
+            '0.param1': plugins[0]['extra_params']['param1'],
+            '0.param2': plugins[0]['extra_params']['param2'],
+            '1.param0': plugins[1]['extra_params']['param0'],
+            '1.param1': plugins[1]['extra_params']['param1'],
+            '1.param3': plugins[1]['extra_params']['param3'],
+
+            # Non-overlapping parameters
+            'param2': plugins[0]['extra_params']['param2'],
+            'param3': plugins[1]['extra_params']['param3'],
+
+            # Intersection of overlapping parameters
+            'param1': {
+                'aliases': ['p1'],
+                'options': ['en'],
+                'default': None,
+                'required': True
+            }
+        }
+
+        result = get_extra_params(plugins)
+
+        for ik, iv in expected.items():
+            assert ik in result
+            for jk, jv in iv.items():
+                assert jk in result[ik]
+                assert expected[ik][jk] == result[ik][jk]
diff --git a/tests/test_blueprints.py b/tests/test_blueprints.py
index 212ce61..633c443 100644
--- a/tests/test_blueprints.py
+++ b/tests/test_blueprints.py
@@ -107,6 +107,7 @@ class BlueprintsTest(TestCase):
         assert isinstance(js, models.Error)
         resp = self.client.get("/api/?i=My aloha mohame&algo=DummyRequired&example=notvalid")
         self.assertCode(resp, 400)
+        self.app.config['TESTING'] = True
         resp = self.client.get("/api/?i=My aloha mohame&algo=DummyRequired&example=a")
         self.assertCode(resp, 200)
 
@@ -148,6 +149,53 @@ class BlueprintsTest(TestCase):
         assert len(js['analysis']) == 1
         assert js['entries'][0]['nif:isString'] == 'My aloha mohame'
 
+    def test_requirements_chain_help(self):
+        '''The extra parameters of each plugin should be merged if they are in a chain '''
+        resp = self.client.get("/api/split/DummyRequired?help=true")
+        self.assertCode(resp, 200)
+        js = parse_resp(resp)
+        assert 'valid_parameters' in js
+        vp = js['valid_parameters']
+        assert 'example' in vp
+
+    def test_requirements_chain_repeat_help(self):
+        '''
+        If a plugin appears several times in a chain, there should be a way to set different
+        parameters for each.
+        '''
+        resp = self.client.get("/api/split/split?help=true")
+        self.assertCode(resp, 200)
+        js = parse_resp(resp)
+        assert 'valid_parameters' in js
+        vp = js['valid_parameters']
+        assert '0.delimiter' in vp
+        assert '1.delimiter' in vp
+        assert 'delimiter' in vp
+
+    def test_requirements_chain(self):
+        """
+        It should be possible to specify different parameters for each step in the chain.
+        """
+
+        # First, we split by sentence twice. Each call should generate 3 additional entries
+        # (one per sentence in the original).
+        resp = self.client.get('/api/split/split?i=The first sentence. The second sentence.'
+                               '\nA new paragraph&delimiter=sentence')
+        js = parse_resp(resp)
+        assert len(js['analysis']) == 2
+        assert len(js['entries']) == 7
+
+        # Now, we split by sentence. This produces 3 additional entries.
+        # Then, we split by paragraph. This should create 2 additional entries (One per paragraph
+        # in the original text)
+        resp = self.client.get('/api/split/split?i=The first sentence. The second sentence.'
+                               '\nA new paragraph&0.delimiter=sentence&1.delimiter=paragraph')
+        # Calling dummy twice, should return the same string
+        self.assertCode(resp, 200)
+        js = parse_resp(resp)
+        assert len(js['analysis']) == 2
+        assert len(js['entries']) == 6
+
     def test_error(self):
         """
         The dummy plugin returns an empty response,\