list_contacts

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

No annotations are provided, so the description carries the behavioral disclosure burden. It does add meaningful context about the account-level scope and the domain definition of a contact, but it does not mention read-only guarantees, authentication requirements, or what data each listed contact contains.

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 one tight, front-loaded sentence with a single parenthetical that adds value without bloat. Every word earns its place, and the key differentiator (account-level vs per-mailbox) is positioned immediately after the verb and resource.

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 list operation with no output schema, this description is largely sufficient. It defines the tool's scope and data model precisely. It could go further by mentioning pagination or the shape of returned contacts, but those are not critical for an agent deciding whether to invoke it.

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 and schema coverage is 100%, so there are no parameter semantics to clarify. The description's scope note adds useful context that would otherwise be absent, and no parameter explanation is needed.

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 clear resource ('contacts'), then sharpens the scope with 'account-level, not per-mailbox'. This immediately distinguishes it from per-mailbox concepts and matches the sibling tool family without ambiguity.

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?

There is no competing list-contacts sibling, but the description clearly states the tool's coverage: account-level contacts across all owned mailboxes, not a single mailbox. This gives an agent enough context to decide when this list tool is appropriate, though it does not explicitly name alternatives or exclusions.

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