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

Goes well beyond the annotations: discloses posting identity (assistant), audience visibility, @-mention notification semantics ("they're told even if they only hear mentions"), and critically the needs_confirmation/approval round-trip the agent must handle. These are operational behaviors an agent could not infer from readOnlyHint/destructiveHint=false.

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 action and audience, then conditioned usage, then the confirmation caveat. The 'write for the room, not for the person who asked' sentence is stylistic guidance that is useful but slightly beyond the definition's core job.

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 adequately covers the confirmation envelope but says nothing about failure modes, rate limits, or whether reposting is safe. For a 4-param write tool whose schema and annotations are already rich, the remaining gaps are minor.

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 already 100%, so the baseline is 3, but the description adds real meaning for `text` (mention syntax via @ plus the name as rooms_list renders it) and for `approvalId` (the confirm-then-resubmit flow from a needs_confirmation envelope). Workspace-scope nuances remain schema-only, which is acceptable.

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 ("Posts a message into a room's stream") plus the authoring identity ("as the assistant") and audience ("everyone in the room will see it"). That combination cleanly separates it from rooms_read, rooms_search, and comments_create without needing to name them.

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?

Gives two concrete triggering conditions: a user asking to share something with a room, or a routine instructed to deliver results to a room other than its default. It doesn't name alternatives (e.g., when to post as a comment instead), so not a full 5, but the usage context is unambiguous.

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