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

Annotations cover the safety profile (non-read-only, idempotent, non-destructive), and the description adds genuinely new behavior: an authentication requirement, a server-signed envelope on success, and structured failure semantics including 'counts_as_invalid' and 'retry_after_s' (implying rate limiting). It stops short of saying what invalid signals cost the caller or how idempotency behaves on retry.

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?

Two dense sentences with the verb and payload kind front-loaded and no filler. The error-field enumeration is compact, though it partially duplicates the output schema.

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?

An output schema exists, so restating return values is not strictly needed; the real gap is the undocumented nested payload object for a write operation. It tells the agent what to send at a high level but not enough to construct a valid signal without inspecting further schema or docs.

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?

There is exactly one parameter, an unconstrained nested object (additionalProperties: true) with 0% schema description coverage. The description hints at a 'kind' field and a signature but never documents required fields, signature placement, or the envelope structure, so the single opaque payload remains essentially undefined.

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 ('Publish a signal') plus the exact payload kind ('m2m-arena/signal/v1') and the signing authority (a delegated signal key). It is clearly distinct from read-side siblings like get_envelopes or verify_object, though it never explicitly names an alternative.

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?

The phrase 'signed by a delegated signal key' implies a prerequisite (the delegate_signal_key sibling) but never says so directly, and there is no explicit when-to-use vs. when-not guidance or comparison to verify_object/canonicalize. Usage is inferable but not stated.

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