send_message

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

No annotations are provided, so the description carries the full load and does so well: it discloses recipient-set snapshot semantics at send time, that an invalid in_reply_to aborts the whole send, and the exact return shape (delivered, recipients, messages with per-copy ids). It omits rate limits, error behavior for unknown recipient names, and any auth/permission detail beyond registration.

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 two addressing modes, then prerequisites and return contract, with no filler. Some sentences are long and clause-stacked (the in_reply_to/readInbox sentence in particular), which slightly hurts scannability.

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 and no annotations, the description correctly compensates by documenting the return payload and the write fan-out. Gaps are modest: failure modes for an unregistered or misspelled recipient name and any delivery guarantees are left unstated.

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 still adds real meaning by defining 'all' as everyone-else broadcast, explaining that the stored copy records the answered id surfaced as inReplyTo by read_inbox/read_conversation/search, and noting the per-recipient copy explosion for broadcasts.

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?

Specific verb and resource (send a message) with an explicit two-mode scope: one named recipient, or 'all' for a broadcast. The broadcast mode is spelled out in the first sentence, which is exactly the distinction an agent needs to pick correctly without opening the 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 a hard prerequisite ('Requires register first') and clarifies when in_reply_to applies and what ids are valid. It does not, however, contrast itself with siblings like ask or post, so an agent must infer that this is the direct/broadcast channel rather than the Q&A or channel-posting path.

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