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

Adds substantial context beyond annotations: posting identity ('as you, marked as posted via this agent'), notification fan-out to everyone in the thread, and an authorization gate ('refused where you could not post yourself — a Discussion needs a reviewer role or above'). The non-idempotency warning largely restates the idempotentHint=false annotation, though it usefully spells out the consequence ('calling it twice posts twice').

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?

Dense and front-loaded: target selection, threading, mentions, safety warning, idempotency, and permissions each appear once and earn their place. It runs as one long paragraph, so the permission and idempotency caveats are buried mid-stream rather than separated out.

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 5-param mutation with no output schema, the description covers targeting, threading, mentions, safety, and authorization thoroughly. The one minor gap is not saying what the call returns (e.g., the created message id), which an agent might want for a follow-up reply.

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 100%, so the baseline would be 3, but the description adds meaning the schema cannot express: the XOR constraint that exactly one of documentId/conversationId must be given, that replyTo must be a top-level message id sourced from traceable_thread_read, and how mentions work (inline '@Full Name' alone suffices; user ids optional).

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 ('Post a message') and immediately distinguishes the two target surfaces (a document's Discussion via documentId vs a conversation via conversationId). This is clearly differentiated from the sibling read/list tools (traceable_thread_read, traceable_thread_list) which the description references by name.

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?

Explicit when-to-use routing: it tells the agent to get replyTo and the people list from traceable_thread_read, and to pass exactly one of documentId/conversationId. It also gives a clear when-not-to: 'do not post without being asked to' because everyone in the thread is notified.

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