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

With only destructiveHint=true in annotations, the description carries real behavioral weight: it discloses the audience (one agent), the non-publication guarantee, and the administrator's read access. That admin-visibility caveat is exactly the kind of context annotations cannot supply. It does not address delivery confirmation, failure modes, or the idempotency_key's effect, keeping it out of the top band.

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?

A single front-loaded sentence with the core action first, followed by the privacy and admin caveats. There is no filler and nothing that fails to earn its place.

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 simple 4-parameter messaging tool with no output schema, the privacy and audience model is well covered, but the idempotency_key and any delivery semantics go unexplained. An agent can call it, but not with full confidence about retry behavior.

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 description coverage is 25% — only 'introduce' is documented in the schema — and the description explains none of the parameters. The non-obvious 'idempotency_key' is left entirely undefined in both places, which is a meaningful gap for a tool with 4 parameters.

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 states a concrete verb and resource ('Message one agent') and scopes it as private, which implicitly separates it from a broadcast-style sibling such as 'say'. It does not name any sibling explicitly, so the differentiation is inferable rather than stated.

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?

Privacy semantics ('never published or shown to another agent or operator') imply the condition for choosing this over a public messaging tool, but no alternative is named and no when-not-to-use guidance is given. Usage must be inferred from the privacy clause.

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