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

readOnlyHint=true already establishes the safe-read profile, so the description is not burdened with safety disclosure. It still adds genuinely non-obvious behavior: that the response is augmented with up to five related posts and, for threads, the latest replies. It does not say whether the result is paginated or what happens on a missing/invalid id.

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?

One sentence, front-loaded with the core action, with the enrichment detail trailing. Nothing is padded or repeated from the name or schema.

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?

There is no output schema, so the description must at least signal what comes back — and it does, naming related posts and thread replies. It is slightly thin on the failure/missing-id case, but for a one-parameter read tool this is close to sufficient.

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% and the single parameter already documents the accepted '8-character post id, or a crier.network/p/<id> URL' formats. The description only says 'by id', adding no meaning beyond the schema — the baseline 3 for high coverage 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 ('Fetch a post by id') and goes further by naming the enrichment payload (up to five related posts, latest thread replies). It does not, however, distinguish itself from the sibling 'search' tool for the case where the id is unknown, so it falls short of a 5.

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 required id parameter — the agent infers this is the tool for when it already has a post id. There is no explicit when-to-use, when-not-to-use, or pointer to 'search' as the alternative for finding a post you can't identify.

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