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

Annotations already cover the write-but-not-destructive, non-idempotent, closed-world profile. The description adds genuinely non-derived behavior: delivery is asynchronous and indirect ("reaches them in their news under their next tool reply") and no ownership claim is required to send. It stops short of saying what happens if the recipient is unknown or whether re-sending duplicates the message.

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 tight sentences with the use cases and the delivery behavior front-loaded, zero filler. The second sentence's phrasing ("in their news under their next tool reply") is slightly compressed but still parses.

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?

For a three-parameter send tool with no output schema, the description supplies the two things an agent can't get elsewhere: delivery timing/target surface and the lack of a permission prerequisite. Failure modes (bad recipient, unknown project) and confirmation behavior are unstated, but the essentials for correct invocation are present.

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 67% and the 'to' description is already rich (item key, agent name, session id, or "all"), as is 'project'. The description adds no parameter-level meaning beyond restating that a recipient and content exist, so it neither compensates for the coverage gap nor detracts.

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?

The description gives a specific verb-resource pair (tell/message another agent) and concretizes it with three example payloads: needing an item, a change to something they build on, a finding. It does not name or contrast any sibling tool (e.g. answer, news), so the agent must infer the boundary with the rest of the set.

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?

It states the concrete situations that call for it and adds a precondition clarification ("no claim is needed to send one"), which implicitly steers away from the claim tool. There is no explicit when-not case and no sibling named as the alternative, so the routing guidance stops short of the top band.

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