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

Goes well beyond the annotations: it discloses the outward side effect (an email is actually sent), the scoping guarantee that audience/status/stats are untouched (elaborating destructiveHint=false), the '[TEST]' subject transform, the contact-existence requirement, and the not_found_emails return field despite no output schema. This is rich disclosure for a write-with-side-effects tool.

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?

Four tight sentences, front-loaded with purpose, then scope guarantees, then recipient constraints, then the usage cue. No filler; every clause (subject prefix, stats immunity, not_found_emails) carries actionable information.

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 2-param tool with no output schema and no annotations covering behavioral scope, the description covers purpose, side effects, non-destructiveness, recipient preconditions, and the return signal. Nothing an agent needs to call it correctly appears to be missing.

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 both parameters are already documented (baseline 3). The description adds real meaning beyond the schema by explaining the consequence for the `emails` parameter when an address is not a contact ('returned in not_found_emails'), which the schema does not state.

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 precise verb+resource+scope: sends a *test copy* of a *broadcast* to *specific email addresses*, and the '[TEST]' subject prefix confirms the intent. The closing line ('preview a real send before launching') implicitly distinguishes it from meisa_send_broadcast, so an agent can tell it apart from the real-send sibling.

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?

Explicit when-to-use is given: 'Use this to preview a real send before launching.' However, it names no alternative tool by name and states no when-not condition (e.g., using it beyond previewing), so routing guidance is clear but not exhaustive.

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