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

Goes well beyond the annotations, which only cover the read-only/idempotent safety profile. It discloses a hard cap ('up to 25 comments'), the nesting shape of replies, and an important exclusion ('Images and files attached to the post are not returned; links typed in the text are') that an agent could not otherwise know without an output schema.

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?

Front-loaded with the core fact and sized appropriately for a two-parameter read tool. The first and second sentences partially repeat the 'full text and comments, replies nested' idea, which is minor waste but keeps the framing clear.

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 no output schema, the description carries the return-shape burden and does so: fields, comment cap, nesting, and media exclusion are all covered. It does not say whether more than 25 comments can be retrieved or what happens when the post_id is invalid, leaving small gaps for a lookup 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% and both parameters are already documented in the schema, including 'post_id or slug'. The description restates the identifier option but adds no new syntax, format, or constraint information, 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?

States a specific verb and resource ('Returns one post by post_id or slug') and enumerates what comes back (title, full text, author, comments with nested replies). This clearly distinguishes it from list_posts, which the agent would otherwise have to infer.

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?

Implies usage by requiring an identifier 'from list_posts', which effectively says fetch a single known post rather than browse. It also routes the reader forward to comment_on_post with a concrete instruction ('Use comment_id as parent_comment_id'), but never explicitly states when not to use it or how it differs from list_posts in prose.

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