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

Goes well beyond the annotations: it explains that the previous text is preserved in edit history, that repeat submissions are idempotent no-ops, that concurrent edits surface as conflicts instead of silent overwrites, and that newly added mentions trigger notifications. This directly qualifies the destructiveHint=true flag by showing the operation is recoverable and never clobbers stale state.

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?

Dense but front-loaded: the primary action and its permission gate lead, and each semicolon clause carries distinct information (history, idempotency, conflict, notifications, endpoint, return shape). The PATCH-path sentence is arguably only useful to API-familiar agents, but nothing is padded.

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 mutating tool with no output schema, the description supplies the authorization model, mutation semantics, failure/idempotency behavior, and even the return shape ({id, kind, number, effect}), which is more than an agent needs to call it correctly. The only unaddressed element, the nested thread parameter, is fully specified in the schema itself.

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 already 80%, so most parameters are self-documenting (body, owner, repo, comment_id with a pointer to merjax_list_pr_comments). The description adds only the 'by comment id' framing and leaves the nested `thread` object (kind/number) and its required-ness unmentioned, so it does not meaningfully extend the schema's coverage.

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?

States a specific verb and resource ('Replace the text of a comment on an issue or pull request') plus the addressing key (comment id). This cleanly separates it from the creation siblings (merjax_comment_issue, merjax_comment_pr) and from merjax_delete_comment without needing to open a schema.

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?

Gives real preconditions: 'Its author or a repository writer only', and describes the no-op case ('the same text again is unchanged') and the conflict case ('never overwritten'), which tells an agent when the call will not do what it expects. It does not explicitly name alternatives such as merjax_delete_comment or merjax_list_pr_comments (the latter only appears in the schema), so routing guidance is implied rather than spelled out.

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