diff --git a/docs/api/earwigbot.tasks.rst b/docs/api/earwigbot.tasks.rst
index 5ab84dc..1e0a50d 100644
--- a/docs/api/earwigbot.tasks.rst
+++ b/docs/api/earwigbot.tasks.rst
@@ -13,5 +13,4 @@ tasks Package
 
 .. automodule:: earwigbot.tasks.wikiproject_tagger
     :members:
-    :undoc-members:
     :show-inheritance:
diff --git a/earwigbot/tasks/wikiproject_tagger.py b/earwigbot/tasks/wikiproject_tagger.py
index e0ae917..1d7d30f 100644
--- a/earwigbot/tasks/wikiproject_tagger.py
+++ b/earwigbot/tasks/wikiproject_tagger.py
@@ -20,14 +20,310 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
+import re
+
+from earwigbot import exceptions
 from earwigbot.tasks import Task
+from earwigbot.wiki import constants
 
 class WikiProjectTagger(Task):
-    """A task to tag talk pages with WikiProject Banners."""
+    """A task to tag talk pages with WikiProject banners.
+
+    Usage: :command:`earwigbot -t wikiproject_tagger PATH
+    --banner BANNER (--category CAT | --file FILE) [--summary SUM]
+    [--append TEXT] [--autoassess] [--nocreate] [--recursive NUM]
+    [--site SITE]`
+
+    .. glossary::
+
+    ``--banner BANNER``
+        the page name of the banner to add, without a namespace (unless the
+        namespace is something other than ``Template``) so
+        ``--banner WikiProject Biography`` for ``{{WikiProject Biography}}``
+    ``--category CAT`` or ``--file FILE``
+        determines which pages to tag; either all pages in a category (to
+        include subcategories as well, see ``--recursive``) or all
+        pages/categories in a file (utf-8 encoded and path relative to the
+        current directory)
+    ``--summary SUM``
+        an optional edit summary to use; defaults to
+        ``"Adding WikiProject banner {{BANNER}}."``
+    ``--append TEXT``
+        optional text to append to the banner (after an autoassessment, if
+        any), like ``|importance=low``
+    ``--autoassess``
+        try to assess each article's class automatically based on the class of
+        other banners on the same page
+    ``--nocreate``
+        don't create new talk pages with just a banner if the page doesn't
+        already exist
+    ``--recursive NUM``
+        recursively go through subcategories up to a maximum depth of ``NUM``,
+        or if ``NUM`` isn't provided, go infinitely (this can be dangerous)
+    ``--site SITE``
+        the ID of the site to tag pages on, defaulting to the... default site
+
+    """
     name = "wikiproject_tagger"
 
-    def setup(self):
-        pass
+    # Regexes for template names that should always go above the banner, based
+    # on [[Wikipedia:Talk page layout]]:
+    TOP_TEMPS = [
+        r"skip ?to ?(toc|talk|toctalk)$",
+
+        r"ga ?nominee$",
+
+        r"(user ?)?talk ?(header|page|page ?header)$",
+
+        r"community ?article ?probation$",
+        r"censor(-nudity)?$",
+        r"blp(o| ?others?)?$",
+        r"controvers(ial2?|y)$",
+
+        r"(not ?(a ?)?)?forum$",
+        r"tv(episode|series)talk$",
+        r"recurring ?themes$",
+        r"faq$",
+        r"(round ?in ?)?circ(les|ular)$",
+
+        r"ar(ti|it)cle ?(history|milestones)$",
+        r"failed ?ga$",
+        r"old ?prod( ?full)?$",
+        r"(old|previous) ?afd$",
+
+        r"((wikiproject|wp) ?)?bio(graph(y|ies))?$",
+    ]
+
+    def _upperfirst(self, text):
+        """Try to uppercase the first letter of a string."""
+        try:
+            return text[0].upper() + text[1:]
+        except IndexError:
+            return text
 
     def run(self, **kwargs):
-        pass
+        """Main entry point for the bot task."""
+        if "file" not in kwargs and "category" not in kwargs:
+            log = "No pages to tag; I need either a 'category' or a 'file' passed as kwargs"
+            self.logger.error(log)
+            return
+        if "banner" not in kwargs:
+            log = "Needs a banner to add passed as the 'banner' kwarg"
+            self.logger.error(log)
+            return
+
+        site = self.bot.wiki.get_site(name=kwargs.get("site"))
+        banner = kwargs["banner"]
+        summary = kwargs.get("summary", "Adding WikiProject banner $3.")
+        append = kwargs.get("append")
+        autoassess = kwargs.get("autoassess", False)
+        nocreate = kwargs.get("nocreate", False)
+        recursive = kwargs.get("recursive", 0)
+        banner, names = self.get_names(site, banner)
+        if not names:
+            return
+        job = _Job(banner, names, summary, append, autoassess, nocreate)
+
+        try:
+            self.run_job(kwargs, site, job, recursive)
+        except _ShutoffEnabled:
+            return
+
+    def run_job(self, kwargs, site, job, recursive):
+        """Run a tagging *job* on a given *site*."""
+        if "category" in kwargs:
+            title = kwargs["category"]
+            title = self.guess_namespace(site, title, constants.NS_CATEGORY)
+            self.process_category(site.get_page(title), job, recursive)
+
+        if "file" in kwargs:
+            with open(kwargs["file"], "r") as fileobj:
+                for line in fileobj:
+                    if line.strip():
+                        line = line.decode("utf8")
+                        if line.startswith("[[") and line.endswith("]]"):
+                            line = line[2:-2]
+                        page = site.get_page(line)
+                        if page.namespace == constants.NS_CATEGORY:
+                            self.process_category(page, job, recursive)
+                        else:
+                            self.process_page(page, job)
+
+    def guess_namespace(self, site, title, assumed):
+        """If the given *title* does not have an explicit namespace, guess it.
+
+        For example, when transcluding templates, the namespace is guessed to
+        be ``NS_TEMPLATE`` unless one is explicitly declared (so ``{{foo}}`` ->
+        ``[[Template:Foo]]``, but ``{{:foo}}`` -> ``[[Foo]]``).
+        """
+        prefix = title.split(":", 1)[0]
+        if prefix == title:
+            return u":".join((site.namespace_id_to_name(assumed), title))
+        try:
+            site.namespace_name_to_id(prefix)
+        except exceptions.NamespaceNotFoundError:
+            return u":".join((site.namespace_id_to_name(assumed), title))
+        return title
+
+    def get_names(self, site, banner):
+        """Return all possible aliases for a given *banner* template."""
+        title = self.guess_namespace(site, banner, constants.NS_TEMPLATE)
+        if title == banner:
+            banner = banner.split(":", 1)[1]
+        page = site.get_page(title)
+        if page.exists != page.PAGE_EXISTS:
+            self.logger.error(u"Banner [[{0}]] does not exist".format(title))
+            return banner, None
+
+        if banner == title:
+            names = [self._upperfirst(banner)]
+        else:
+            names = [self._upperfirst(banner), self._upperfirst(title)]
+        result = site.api_query(action="query", list="backlinks", bllimit=500,
+                                blfilterredir="redirects", bltitle=title)
+        for backlink in result["query"]["backlinks"]:
+            names.append(backlink["title"])
+            if backlink["ns"] == constants.NS_TEMPLATE:
+                names.append(backlink["title"].split(":", 1)[1])
+
+        log = u"Found {0} aliases for banner [[{1}]]".format(len(names), title)
+        self.logger.debug(log)
+        return banner, names
+
+    def process_category(self, page, job, recursive):
+        """Try to tag all pages in the given category."""
+        self.logger.info(u"Processing category: [[{0]]".format(page.title))
+        for member in page.get_members():
+            if member.namespace == constants.NS_CATEGORY:
+                if recursive is True:
+                    self.process_category(member, job, True)
+                elif recursive:
+                    self.process_category(member, job, recursive - 1)
+            else:
+                self.process_page(member, job)
+
+    def process_page(self, page, job):
+        """Try to tag a specific *page* using the *job* description."""
+        if job.counter % 10 == 0:  # Do a shutoff check every ten pages
+            if self.shutoff_enabled(page.site):
+                raise _ShutoffEnabled()
+        job.counter += 1
+
+        if not page.is_talkpage:
+            page = page.toggle_talk()
+        try:
+            code = page.parse()
+        except exceptions.PageNotFoundError:
+            if job.nocreate:
+                log = u"Skipping nonexistent page: [[{0}]]".format(page.title)
+                self.logger.info(log)
+            else:
+                log = u"Tagging new page: [[{0}]]".format(page.title)
+                self.logger.info(log)
+                banner = "{{" + job.banner + job.append + "}}"
+                summary = job.summary.replace("$3", banner)
+                page.edit(banner, self.make_summary(summary))
+            return
+        except exceptions.InvalidPageError:
+            log = u"Skipping invalid page: [[{0}]]".format(page.title)
+            self.logger.error(log)
+            return
+
+        for template in code.ifilter_templates(recursive=True):
+            name = self._upperfirst(template.name.strip())
+            if name in job.names:
+                log = u"Skipping page: [[{0}]]; already tagged with '{1}'"
+                self.logger.info(log.format(page.title, name))
+                return
+
+        banner = self.make_banner(job, code)
+        shell = self.get_banner_shell(code)
+        if shell:
+            if shell.has_param(1):
+                shell.get(1).value.insert(0, banner + "\n")
+            else:
+                shell.add(1, banner)
+        else:
+            self.add_banner(code, banner)
+        self.apply_genfixes(code)
+
+        self.logger.info(u"Tagging page: [[{0}]]".format(page.title))
+        summary = job.summary.replace("$3", banner)
+        page.edit(unicode(code), self.make_summary(summary))
+
+    def make_banner(self, job, code):
+        """Return banner text to add based on a *job* and a page's *code*."""
+        banner = "{{" + job.banner
+        if job.autoassess:
+            classes = {"fa": 0, "fl": 0, "ga": 0, "a": 0, "b": 0, "start": 0,
+                       "stub": 0, "list": 0, "dab": 0, "c": 0, "redirect": 0,
+                       "book": 0, "template": 0, "category": 0}
+            for template in code.ifilter_templates(recursive=True):
+                if template.has_param("class"):
+                    value = unicode(template.get("class").value).lower()
+                    if value in classes:
+                        classes[value] += 1
+            values = tuple(classes.values())
+            best = max(values)
+            confidence = float(best) / sum(values)
+            if confidence > 0.75:
+                rank = tuple(classes.keys())[values.index(best)]
+                if rank in ("fa", "fl", "ga"):
+                    banner += "|class=" + rank.upper()
+                else:
+                    banner += "|class=" + self._upperfirst(rank)
+        return banner + job.append + "}}"
+
+    def get_banner_shell(self, code):
+        """Return the banner shell template within *code*, else ``None``."""
+        regex = r"^\{\{\s*((WikiProject|WP)[ _]?Banner[ _]?S(hell)?|W(BPS|PBS|PB)|Shell)"
+        shells = code.filter_templates(matches=regex)
+        if not shells:
+            shells = code.filter_templates(matches=regex, recursive=True)
+        if shells:
+            log = u"Inserting banner into shell: {0}"
+            self.logger.debug(log.format(shells[0].name))
+            return shells[0]
+
+    def add_banner(self, code, banner):
+        """Add *banner* to *code*, following template order conventions."""
+        index = 0
+        for i, template in enumerate(code.ifilter_templates()):
+            name = template.name.lower().replace("_", " ")
+            for regex in self.TOP_TEMPS:
+                if re.match(regex, name):
+                    self.logger.info("Skipping top template: {0}".format(name))
+                    index = i + 1
+
+        self.logger.debug(u"Inserting banner at index {0}".format(index))
+        code.insert(index, banner)
+
+    def apply_genfixes(self, code):
+        """Apply general fixes to *code*, such as template substitution."""
+        regex = r"^\{\{\s*((un|no)?s(i((gn|ng)(ed3?)?|g))?|usu|tilde|forgot to sign|without signature)"
+        for template in code.ifilter_templates(matches=regex):
+            self.logger.debug("Applying genfix: substitute {{unsigned}}")
+            template.name = "subst:unsigned"
+
+
+class _Job(object):
+    """Represents a single wikiproject-tagging task.
+
+    Stores information on the banner to add, the edit summary to use, whether
+    or not to autoassess and create new pages from scratch, and a counter of
+    the number of pages edited.
+    """
+    def __init__(self, banner, names, summary, append, autoassess, nocreate):
+        self.banner = banner
+        self.names = names
+        self.summary = summary
+        self.append = append
+        self.autoassess = autoassess
+        self.nocreate = nocreate
+        self.counter = 0
+
+
+class _ShutoffEnabled(Exception):
+    """Raised by process_page() if shutoff is enabled. Caught by run(), which
+    will then stop the task."""
+    pass