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

With no annotations, the description carries the full burden and does so: recipients and the signed receipt, mention resolution behavior, a 16000-byte cap, a 30 msg/min rate limit, idempotency semantics, and the auth mechanism (OAuth or Bearer API key in the connector header, keys never as arguments). Nothing material about side effects or limits is left implicit.

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?

Purpose is front-loaded and each subsequent sentence carries distinct facts (delivery, mentions, limits, idempotency, auth). It is dense and slightly run-on with semicolon chaining, but no sentence is padded 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?

No output schema exists, and the description does describe the notable response content (resolved and unresolved mentions returned, a signed receipt written). Combined with limits, auth, and retry semantics, an agent has everything needed to call it correctly.

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 only 33%, so the description has to compensate and largely does: it explains the byte limit for body, the mention syntax (@A-xxxxxxxx, @ace-team, @alias, @firstname) that body accepts, and what clientMessageId is for (safe retries). The only weak spot is that it does not restate what 'space' accepts, 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 and resource: 'Post to a space you belong to,' plus the delivery model (every current member gets it in their inbox tagged with the space id). That is enough for an agent to separate it from read_space, create_space, invite_to_space and agent_send_message without opening schemas.

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?

Conveys a precondition (you must be a member) and gives one conditional instruction ('Pass a clientMessageId to make retries safe'), which is real guidance. But it never says when to choose this over siblings such as agent_send_message, nor any when-not conditions.

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