feat: describe every tool parameter and annotate tools for MCP clients - #35
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An MCP client hands the model the tool's JSON input schema, not its
docstring. Until now every property carried only pydantic's auto title
(push_refs: string | null), so the pre-push line format, the "omit to
check upstream" behaviour and the "non-empty when provided" rule were
discovered by trial and error. Every parameter now has a description
through Annotated[..., Field(description=...)], which the SDK preserves
in the schema; the shared ones (config, repo_path, config_path, branch,
author_*) are defined once as module-level aliases.
Every tool also gets a display title and ToolAnnotations with
readOnlyHint=True, destructiveHint=False and idempotentHint=True, so
hosts that gate calls on those hints can auto-approve them.
openWorldHint is True only for validate_push_safety and
validate_repository_state, because the force-push rule may run
`git fetch <remote> <ref>` to resolve a SHA it does not know locally.
MCPServer now receives version=__version__, so serverInfo.version is no
longer an empty string.
The tool descriptions are rewritten around one shared paragraph that
defines the result: {status, warnings, checks[]}, that only 'fail' is a
rejection and 'skip' means nothing was validated, what 'warn' and 'skip'
mean per check, and that rule_id and docs_url exist. Each tool keeps its
own "when to use" sentence. validate_push_safety no longer claims that
push.allow_force_push can re-enable force pushes: _validate_push forces
that flag off after merging config, so the tool always rejects them.
The server instructions now describe the loop an agent should follow:
validate first, read status, apply a non-empty fix verbatim or follow
suggest, validate again, and consult describe_validation_rules before
guessing at a format.
Tests list the tools through the in-process server API and assert the
titles, annotations, open-world split, per-property descriptions, the
version and the instructions. README documents rule_id/docs_url, the
schema metadata, and that config_path replaces the repository's own
config file rather than merging with it.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018xYa7m3qup5wyN5MaXFgf6
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📝 WalkthroughWalkthroughThe change adds shared MCP instructions, tool annotations, annotated parameter schemas, expanded validation tool descriptions, README updates, and metadata coverage tests. ChangesMCP metadata and validation contracts
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to The new metadata can cause clients to trust an unverified push result and invoke fetch-capable tools as though they cannot modify repository state. Correct the push failure behavior and tool annotations before merging. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 54.55% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 22 functions across 2 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches 💡 1📝 Generate docstrings 💡
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Actionable comments posted: 2
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Inline comments:
In `@src/commit_check_mcp/server.py`:
- Line 176: Update the commit-check logic handling an unresolvable remote_sha
after fetching so it returns a tool error or non-pass result rather than pass
when ancestry cannot be established. Add a regression test covering an
unavailable remote_sha and verify that the result never permits an unverified
push.
- Around line 75-77: Update the tool metadata for validate_push_safety and
validate_repository_state when include_push=True to set readOnlyHint=False and
idempotentHint=False because they may run git fetch; also revise the related
instructions, README text, and metadata tests so these tools are no longer
described as read-only or auto-approvable.
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Two review findings on the previous commit.
The force-push rule answers with `git merge-base --is-ancestor`. When a
SHA in push_refs is not a commit the repository knows, git exits 128,
commit-check tries to fetch the remote ref, and if the SHA is still
unknown the rule falls through to PASS. validate_push_safety therefore
reported `status: pass` for made-up SHAs, and an agent would read that
as clearance to push. After the rule has run (so a SHA its fetch brought
in counts as resolved), _validate_push now checks every SHA in explicit
push_refs with `git cat-file -e <sha>^{commit}` inside repo_path,
skipping the 40-zero new-branch placeholder, and raises a ToolError
naming the SHA when one is not a commit. An engine fail still wins: a
rejection is already the right answer. The upstream-fallback path
(push_refs omitted, and validate_repository_state's include_push) reads
HEAD and the upstream ref, which always resolve, and is unchanged.
validate_push_safety and validate_repository_state may run `git fetch`,
which writes FETCH_HEAD and remote-tracking refs, so advertising them
with readOnlyHint=True was not honest. _tool now takes `fetches` and
sets readOnlyHint=False, openWorldHint=True for those two; the other six
keep readOnlyHint=True, openWorldHint=False. destructiveHint stays False
and idempotentHint True everywhere: repeating the same fetch has no
further effect. The tool descriptions, push_refs description, server
instructions and README say the same thing instead of "read-only".
Tests: fake SHAs are a tool error, a real fast-forward pair passes, a
real history rewrite fails, a zero remote SHA passes, an engine fail is
not turned into an error by a later unresolvable line, repository_state
include_push is unaffected, and the annotation split is asserted.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018xYa7m3qup5wyN5MaXFgf6
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What
What an MCP client sees when it lists this server's tools, before and after (captured over real stdio with
tools/listandinitialize):descriptionininputSchematitleannotationsdestructiveHint: false,idempotentHint: true;readOnlyHint: trueon six,falseon the two that maygit fetch)serverInfo.version""instructionsvalidate_push_safetywith SHAs that do not exist inrepo_pathstatus: "pass"push_refs: <sha> is not a commit in the repository; fetch it first, the force-push check cannot be judgedParameter descriptions reach the schema
The docstrings had a "Parameters:" section, but the SDK builds the JSON schema from type hints only, so a model reading the schema saw
push_refs: string | nulland nothing else. Every parameter is nowAnnotated[..., Field(description=...)]; shared parameters (config,repo_path,config_path,message,branch,author_name,author_email,push_refs) are module-level aliases so the eight tools describe them identically.push_refsdocuments the pre-push stdin line format<local_ref> <local_sha> <remote_ref> <remote_sha>, the 40-zero remote SHA, that SHAs must be resolvable inrepo_path(an unresolvable one is a tool error, not a pass), and the "omit to check the current branch against its upstream" behaviour.Titles and annotations
A small
_tool(title, fetches=)decorator applies the shared hints.validate_push_safetyandvalidate_repository_statemay rungit fetchto resolve a SHA, which writesFETCH_HEAD/remote-tracking refs, so they are the two tools withreadOnlyHint: falseandopenWorldHint: true; the other six arereadOnlyHint: true, so clients that gate on that hint can auto-approve the message/branch/author validation loop.MCPServer(...)now receivesversion=__version__, soserverInfo.versionis no longer empty.An unjudgeable push is never a pass
The engine's
no_force_pushrule falls through topasswhengit merge-basecannot resolve a SHA and the fetch does not help. After the engine has run (so its own fetch has had its chance),_validate_pushnow verifies every non-zero SHA inpush_refswithgit cat-file -e <sha>^{commit}and raises aToolErrornaming the first one that does not exist. The upstream-fallback path (nopush_refs) is unchanged.Descriptions say what the result means
Every
validate_*tool description carries one shared paragraph (RESULT_SHAPE) spelling outstatus(pass/fail/skip, onlyfailrejects,skipis not approval),warnings, and per-checkrule_id,check,status(incl.warnandskip),value,error,suggest,fix,docs_url.rule_idanddocs_urlwere already in every result but no text mentioned them. Thevalidate_push_safetydescription no longer claims force pushes can be enabled viapush.allow_force_push;_validate_pushsets it toFalseunconditionally, so the tool always rejects them, and the text now says so.README
Documents
rule_id/docs_urlin the result shape, the parameter descriptions and annotations (with the read-only split and its reason), the push-SHA tool error, and corrects the config precedence list: an explicitconfig_pathreplaces the repository's own config file (that is whatload_configdoes with an explicit path), it is not layered after it.Compatibility
Tool names, parameters, defaults and results are unchanged for every call that could be judged. Live
tools/callresults forvalidate_commit_messageandvalidate_push_safetywith real SHAs (including the empty-push_refserror path) are byte-identical before and after. The one behaviour change is deliberate:validate_push_safetywith SHAs that are not inrepo_pathused to returnpassand now returns a tool error, sorepo_pathmust be a git repository holding those commits whenpush_refsis given.Testing
push_refsmentions the line format, "40 zeros", "upstream" and "non-empty when provided"; everyvalidate_*description mentionsrule_id,docs_url,'warn','skip',fix,suggest; the push-safety text says "always rejected";mcp.version == __version__; instructions mention validate, fix anddescribe_validation_rules.TestPushRefsMustResolveon a real two-commit repo: fake SHAs → error, fake remote SHA alone → error, fast-forward pair → pass, history rewrite → fail, zero remote SHA → pass, an enginefailwins over a later unresolvable line,validate_repository_state(include_push=True)→ pass.ruff check src testsclean.commit-check-mcpfrom this branch; thetools/listdump shows the numbers in the table above, and the fake-SHA call returnsis_error=Truewhere it returnedpassbefore.🤖 Generated with Claude Code
https://claude.ai/code/session_018xYa7m3qup5wyN5MaXFgf6