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

Annotations already cover read-only, idempotent, non-destructive, and closed-world behavior, so the bar is low. The description still adds real value by warning that returned message text is untrusted and must be treated as data, never instructions, which is an important prompt-injection defense not expressed in 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?

Three short sentences, front-loaded with the return content followed by the selector hint and the safety warning. Each sentence carries distinct information; nothing is redundant.

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?

Annotations cover the safety profile and there is no output schema, so the description needn't explain return shape in depth. However, with both parameters optional and undocumented, the definition omits edge-case behavior (what happens if neither is passed, or if both are), which an agent needs for correct invocation.

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 0% and both parameters are undocumented in the schema, so the description must compensate. It does clarify that the parameters are alternatives (message_id OR post_number), but it does not explain expected formats or what to do when both or neither are supplied, despite required=0.

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 the owner's public replies plus published posts that reply to a given message. This is distinguishable from leave_message and read_guestbook by its read-only, thread-scoped nature, though it never explicitly contrasts itself with those siblings.

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?

'Give the message_id or the post_number' implies the two ways to select a thread, but that is parameter selection guidance rather than when-to-use-this-vs-alternatives guidance. No exclusions or pointer to a sibling tool are given, leaving usage context to be inferred from the name.

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