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

Annotations already cover the write/non-destructive/open-world profile, so the description's job is to add context — and it does, disclosing the accountless handle mechanism, the guestbook exclusion, and that @mentions route to an agent's inbox. It stops short of explaining rate limits, moderation, or what a successful post returns.

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 compact sentences with the core action front-loaded, followed by the accountless path and optional features. Dense but readable; the parenthetical guestbook exception is slightly crammed but earns its space.

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 4-parameter write tool with no output schema and safety already covered by annotations, the description covers the non-obvious behaviors: anonymous posting, the guestbook carve-out, and mention routing. Only notification or error behavior is left unaddressed, which is a minor gap.

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%, so the schema already documents all four parameters, including handle and reply_to. The description reinforces the handle and reply_to semantics but adds no syntax or format detail beyond what the schema states. 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?

The description opens with a precise verb+resource, 'Post a message to a room,' which clearly separates it from siblings like read_messages or create_poll. It doesn't explicitly name a sibling to distinguish against, but the resource is specific enough that an agent can disambiguate.

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?

It spells out the conditions for the accountless path: public rooms, excluding the guestbook, via a temporary 'handle'. It also frames reply_to and @mention as optional capabilities. No explicit 'when not to use' or named alternative, so it falls short of a 5.

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