List Senders

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

Annotations already declare the operation as read-only, idempotent, and non-destructive. The description adds behavioral nuance by specifying 'verified' senders and 'all', indicating that unverified senders are not returned and that the listing is comprehensive. This goes beyond annotation coverage.

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?

The description is a single sentence with no filler: 'List all verified senders'. It front-loads the verb and object and every word adds meaning.

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 zero-parameter, read-only listing tool, the description plus annotations are sufficient. The 'verified' scope is important and captured. The absence of an output schema is acceptable since 'list' implies a collection result, and no safety caveats are 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?

The tool has zero parameters, so schema coverage is 100% by definition and no parameter documentation is needed. Per the baseline for zero-parameter tools, this is fully adequate.

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 ('list') and a clearly scoped resource ('verified senders'), making the tool's function unambiguous. It distinguishes itself from sibling tools like create_sender and delete_sender, and from other list_* tools which target different resources (email_lists, segments, contacts, etc.).

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 clearly implies when to use this tool: whenever an agent needs to enumerate verified senders. While it doesn't explicitly name alternatives or exclusions, no sibling tool overlaps with listing senders, so the route is clear without explicit guidance.

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