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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds only pagination and filter scope, which the schema already carries, and says nothing about default sort order, result shape, or rate limits.

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?

A single front-loaded sentence with no filler, and the core purpose precedes the filter enumeration. Slightly list-like, but every clause maps to real parameters.

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?

With 16 optional parameters and no output schema, the description is thin: it never mentions the free-text search, the structured filters array, or how match=or interacts with filters. The schema covers these, so an agent can still call it correctly, but the description does not round out the picture for a fairly complex 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 coverage is 75%, so the schema already documents most parameters, and the description's filter list (status, recipient, sender, subject, domain, API key, date) maps onto rcpt_to, mail_from, subject, api_key_id, sending_domain_id and the date fields. It adds no semantics for search, sort, order, match, or the structured filters array, so it does not exceed the schema baseline.

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?

States a specific verb and resource ('List ... emails') and adds scope ('sent and received') that maps to the inbound/outbound type filter. An agent can distinguish it from get-email, but the description does not name any sibling or note how it differs from list-events or the bulk email getters.

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?

Usage is implied by the enumeration of filter dimensions, which signals this is the browsing/search tool for the email collection. There is no explicit when-to-use guidance, no mention of when to prefer get-email for a single message, and no stated prerequisites.

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