Contributor summary

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description does add real context beyond that: counts are computed on HEAD only, not all refs, and output is ordered by activity. It omits that merge commits are excluded by default, a behavior that materially changes the counts.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences, zero filler, with the core scope constraint (HEAD, last N days) and ordering front-loaded before the optional path restriction.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present, return values need no explanation, and the annotations cover the safety profile, so the description's scope details are largely sufficient. The one gap is silent merge-commit handling, which a caller counting commits would want flagged.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so days, path, repo, limit and includeMerges are all documented in the schema. The description only echoes the days window and path restriction, adding no syntax or semantics beyond what the schema already carries. Baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb (count) plus resource (commits per author), with scope (HEAD, last N days) and ordering (most active first) stated up front. An agent can distinguish this aggregation tool from commit_search or recent_activity, though the description never names or contrasts a sibling explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use guidance and no mention of alternatives among the many commit-history siblings (recent_activity, commit_search, file_hotspots). The per-author framing implies its use case but leaves the agent to infer when to pick it over neighbors.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.