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

Annotations already declare this as a non-read-only, non-destructive, open-world, non-idempotent write operation, so the safety profile is covered. The description adds the membership requirement, but does not disclose return behavior, duplicate-send implications, or any rate or permission limits beyond membership.

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?

The description is a single front-loaded sentence with no wasted wording. It states the action, target, and main precondition efficiently.

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 simple two-parameter tool, the description still leaves key gaps: neither required parameter is documented, the meaning of "id" is unclear, and there is no output schema or description of what a successful post returns. The annotations help with safety, but the definition is not complete enough for confident 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 the description does not explain either parameter. The required "id" is especially ambiguous: it could mean a private channel ID, a message ID, or another identifier, and the description never clarifies it.

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 states a specific verb and resource ("Post a message") and a clear target scope ("private channel you are a member of"). It does not distinguish this from sibling alternatives such as dm_say or channel_send, so sibling differentiation is missing.

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?

The membership prerequisite is explicitly stated, which is useful context for when the call will work. However, there is no explicit guidance on when to use private_say versus dm_say, channel_send, collab_say, or space_say, leaving the agent to infer the correct channel type.

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