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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description still adds real behavioral context: aggregation granularity (month-by-month), scope (whole account, not one mailing), and the exclusion rule '(test mailings excluded).' It stops short of 5 because it doesn't say what period is used when 'range' is omitted (a real ambiguity given zero required params).

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 sentence, front-loaded with the core concept (month-by-month, whole-account response stats) followed by a compact metric enumeration. Every clause carries information; nothing is redundant.

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 read-only, zero-required-parameter aggregation tool with 100% schema coverage and no output schema, the description supplies enough: metric set, granularity, scope, and the test-mailing exclusion. The only missing piece an agent would want is the default date window when 'range' is omitted.

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%, with 'range' documented as YYYY-MM-DD~YYYY-MM-DD with one side optional and 'include_deleted' as including archived mailings, so the baseline is 3. The description adds nothing about either parameter, and notably never clarifies the default window when 'range' is absent or how 'include_deleted' relates to the stated test-mailing exclusion.

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 resource with an explicit scope: 'Month-by-month response statistics for the whole account,' which the colon-list of metrics (mailings, sent, delivered, bounced, opened, clicked, forwarded, opt-outs, sign-ups) further pins down. The account-wide scope implicitly separates it from the per-mailing sibling emma_get_mailing_response, but no sibling is named, so it stops short of a 5.

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 only implied: an agent can infer 'use this for a full-account, per-month rollup rather than a single mailing.' There is no explicit when-to-use, no named alternative, and no statement about when this summary is or is not the right tool.

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