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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safe read-only nature. The description adds some functional context (mailbox folder, optional search) but does not describe return shape, pagination behavior, or sorting. This is adequate but not enriched beyond annotations.

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 concise sentences with no filler. The first sentence states the core function, and the second provides a direct pointer to an alternative tool. Every word earns its place.

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 listing tool with three optional parameters and strong annotations, the description covers the key context: what is listed, where it is listed from, optional search, and when to use a different tool. No output schema exists, but the tool's behavior is straightforward enough that this is acceptable.

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%, and each parameter already has a meaningful description. The tool description adds minimal semantic value beyond the schema, mentioning full-text search and mailbox folder but not providing new parameter-level detail. Baseline 3 is appropriate.

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 clearly states the tool 'List emails from a mailbox folder with optional full-text search across subject and body', using a specific verb and resource. It distinguishes itself from the sibling tool list_campaigns by explicitly directing marketing sends elsewhere.

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 explicit usage context: 'Use this for reading the unified inbox; use list_campaigns for marketing sends.' This names an alternative and clarifies when not to use this tool, giving clear guidance beyond what the schema alone provides.

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