Addresses removed from sending

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false. The description adds valuable behavioral context by disclosing that sending to these addresses is refused, and that the output includes the reason for exclusion. This goes beyond the annotation-only information.

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 sentences, no fluff, with the most important scoping information front-loaded. The operational warning is succinctly added at the end.

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 read-only list, the description gives the essential purpose and a usage tip, but it lacks parameter semantics and return-structure details. Since there is no output schema, the agent does not know what the response contains beyond 'reason for each'. Some gaps, but not severe for a filtering list tool.

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 only 25% (only the `since` parameter has a description). The description does not compensate by explaining `limit`, `cursor`, or the `reason` filter, despite the low coverage. The meaning of these parameters is left to inference from names and enum values.

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 and resource: 'List addresses excluded from sending', and enumerates the categories (hard bounces, complaints, unsubscribes) with the reason for each. This clearly distinguishes it from sibling tools like list_messages or get_message because it focuses on bounces and exclusion reasons.

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 gives clear actionable context: 'Sending to one of them is refused, so read this before retrying a failed recipient.' This tells the agent when to use it, though it does not explicitly name sibling alternatives or state when not to use it.

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