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

The readOnlyHint annotation already covers the safety profile, so the description only needs to add context. It does so by disclosing the shape of the result (which requirements are tested, which aren't, and the percentage) plus the branch-scoping behavior, which matters because no output schema exists to convey the return values.

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 short sentences, front-loaded with the core purpose followed by the optional modifier, with no filler or redundancy.

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?

For a two-parameter read-only tool with no output schema, the description covers purpose, filter, and result content adequately. It could go slightly further by noting scope limits (e.g., how untested requirements are counted or whether coverage is recursive), but nothing critical for invocation is missing.

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 both parameters are fully documented in the schema. The description's 'optionally filter by git branch' merely restates the branch parameter without adding syntax, defaults, or edge-case behavior, so the 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?

The description states a specific verb and resource (get aggregate test coverage for a project's requirements) and enumerates what the result contains: tested, untested, and the coverage percentage. This scopes it clearly against the sibling get-requirement-coverage, which is per-requirement rather than aggregate-per-project.

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?

Usage is only implied by the purpose statement; there is no explicit when-to-use, when-not-to-use, or named alternative despite get-requirement-coverage being a plausible sibling. The branch filter is a parameter detail rather than routing guidance.

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