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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description correctly spends its budget elsewhere: the three-tier access model, the reason subject/snippet come back null, the warning that a page may be shorter than per_page, and an explicit prompt-injection caution. The only real gap is that it doesn't state total-count or end-of-results behavior when paging.

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?

Four sentences, front-loaded with scope and ordering, then the status vocabulary, then the access/null contract, then the injection warning. Nothing repeats the schema verbatim and every sentence changes how an agent would read the results.

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?

Output schema exists, yet the description still explains the one genuinely confusing aspect of the payload (access tiers driving null subject/snippet), so an agent won't mistake redaction for missing data. With 10 optional params fully documented in schema, nothing material is left unstated.

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 100%, so baseline is 3, but the description adds the access model that explains why filtering and reading behave differently per row, which is meaning the schema doesn't supply. It also enumerates the status values in prose, which largely restates the enum, keeping this just above 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 plus the exact scope: "emails the current user may see, newest first: synced and sent mail, plus the user's own drafts and outbox." That scope plus the ordering clause cleanly separates it from get-email-tool (single message) and list-email-accounts-tool (accounts, not messages) without either schema being opened.

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 establishes context for browsing mail but never says when to prefer this over get-email-tool for a known message, or over search-style siblings. Usage is implied by the scope sentence rather than stated as a rule, and no exclusions are given.

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