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

The description goes well beyond the annotations by disclosing that this is an 'additive write' (non-destructive), attempted once through a specific endpoint, and that it readback verifies via the immutable comment ID. It also communicates the lack of merge/review capability. This adds meaningful behavioral context without contradicting the annotations.

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?

The description is a single, well-structured paragraph that front-loads the primary purpose and uses each sentence to add value: action, mechanics, verification, and exclusion. There is no wasted text or repetition of schema annotations.

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?

The description provides enough context for an agent to decide when and how to invoke the tool: it identifies the endpoint, notes the write authorization requirement, explains readback verification, and disambiguates from review/merge operations. It could mention expected side effects or rate limits, but given the output schema and annotations, the description is largely complete for this simple mutation tool.

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 coverage is 100%, so the baseline is 3. The description does not add parameter-specific details beyond what the schema already provides; it mentions 'body' and 'Markdown comment' but the schema already describes these. It does not compensate for any coverage gaps since there are none.

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 opens with 'Additive write' and uses a specific verb 'post' to state it creates a comment on a specified issue or pull request. It clearly defines the resource (issue/PR), the content (bounded Markdown comment), and the mechanism (issue-comments REST endpoint). It also distinguishes itself from siblings by stating 'It is not a formal pull-request review and cannot merge.'

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?

The description gives clear context on when to use this tool (to comment on an issue or PR) and explicitly excludes the review/merge capability, guiding an agent away from using it for those purposes. It doesn't explicitly name alternative tools, but the exclusion is enough to differentiate it from related siblings like gh_comment_pr_review or gh_merge_pr.

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