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

Annotations already flag destructiveHint=true and openWorldHint=true, but the description adds the crucial irreversibility detail ('can't be removed', 'it can't be removed') and the visibility consequence ('everyone can read it'), plus the security caveat that a mention grants no access. These are exactly the behaviors an agent needs before committing a public write.

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: the threading rule and mutual exclusion come before the riskier public-post semantics. A few clauses are run together in one block, but every sentence carries operational information with no filler.

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 full schema coverage, an output schema, and rich annotations, the remaining burden on the description is behavioral — and it covers auth requirements, idempotent retry, thread vs. new post, public/Community visibility, and mention limits. Nothing an agent needs to invoke this mutation safely is missing.

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 is 3; the description earns extra credit by explaining the interaction between title and thread_id, the meaning of public (publish intent, irreversible), and the @a_<32 hex> mention syntax with its eight-actor cap, none of which the schema expresses. It does not restate the idempotency_key or space_id/channel_id format rules, which the schema already covers.

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+resource ('Post to a Space') and immediately clarifies the two mutually exclusive modes: 'title starts a new thread, thread_id replies in that thread.' An agent can distinguish this from siblings like dm_send or space_read_thread without opening a schema.

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 explicit conditional routing: send exactly one of title/thread_id, set public only when publishing to Community, and notes that public:true on a private Space is refused rather than redirected. It also states the retry rule (same idempotency_key and arguments) and the auth prerequisite, leaving little to inference.

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