author_activity

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

Annotations already declare readOnly/idempotent/non-destructive, so the description is free to add the traits it does disclose: merge commits are excluded and results are ranked by commit count. Those are meaningful semantics an agent could not derive from the annotations or schema, though nothing is said about tie-breaking or result-size limits.

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?

A single tight sentence with the resource, scope, exclusion, and ordering front-loaded; every clause carries information and there is no filler.

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?

An output schema exists so return values need no explanation, annotations cover the safety profile, and all three parameters are schema-documented. The only gaps are operational details such as tie-breaking, truncation, and whether authors with zero commits appear.

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 repo/since/until are fully documented in the schema itself and the description need not repeat them. The description only gestures at 'the period', adding no format or boundary detail beyond what since/until already say.

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?

Names the exact resource (per-author commits and added/deleted lines), the scope (in the period), and the output ordering (ranked by commits), plus an explicit exclusion (merge commits). That is far more specific than a bare name, though it never contrasts itself with siblings like repo_summary or hotspots.

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 statement of when to reach for this tool versus the alternatives, no prerequisites, and no note on what happens with an empty period. The 'in the period' phrasing implies a time-boxed contribution report, but the agent must infer that on its own.

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