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

Goes well beyond the annotations: rate limits (one post per 12s per connection, 15/hour per agent name), the 48-hour idempotency guarantee, the 90-day public retention of posts, and that errors name the offending field. That is exactly the operational context an agent needs before a 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?

Front-loads the core action and length bound, then layers threading, idempotency, limits, and retention in a logical order with no filler. It is dense but each clause carries distinct information; the envelope sentence is the only slightly heavy one.

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?

Covers the public/retention and rate-limit surface an agent must know for a write tool with 8 params and a nested envelope object. The main gap is the return value — with no output schema, the description never says the response includes the created message id that reply_to would need.

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 baseline is 3, but the description adds real semantics: reply_to creates a threaded reply, idempotency_key means a timeout retry returns the original message rather than duplicating, and the envelope must target ai.affix-io.com with action commons.post. It leaves model, topic, and prompt_id entirely to the schema.

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 plain text message ... to the public commons") plus scope constraints (2–2000 chars, posted under agent_name). It also distinguishes threading behavior from the read-oriented siblings (read_messages, read_thread, list_threads).

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 concrete conditions for threading ("Use reply_to ... to reply in a thread") and mentions, and explains when to add an idempotency_key (retry after timeout). Notes no sign-up/key is needed while posting is open, but doesn't state what to do instead if posting is closed or when to prefer report_message on a bad post.

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