Check recipients against the allowlist

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

The annotations already indicate a read-only, idempotent, non-destructive operation. The description adds valuable behavioral guarantees beyond that by stating 'Nothing is sent and no connection is made,' which meaningfully reduces the agent's concern about side effects. It also clarifies that the tool provides refusal reasons, not just a boolean result.

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?

Three sentences, each earning its place: the first states the core behavior, the second emphasizes side-effect safety, and the third gives usage guidance. The most important functional information is front-loaded, with no filler or redundancy.

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 tool with a single well-documented parameter and an output schema, this description is complete. It covers what the tool does, what it guarantees about side effects, and when it should be used. There are no significant gaps that would prevent an agent from selecting and invoking it correctly.

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 100%, so the addresses parameter is already fully documented in the schema. The description refers to 'given addresses' but does not add additional semantic detail about the parameter format, constraints, or edge cases beyond what the schema provides, warranting the baseline score.

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 uses a specific verb ('Says which') and clearly identifies the resource (given addresses the server is allowed to write to) and the outcome (which are allowed and why others are refused). It effectively distinguishes this from the sibling tools, which focus on server info, message preview, and connection testing.

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 description explicitly tells the agent to use this before composing a message and contrasts it with discovering the refusal afterward. It gives clear timing and context, though it does not explicitly name alternative tools or state when not to use it beyond that timing guidance.

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