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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety profile is covered. The description adds useful behavioral context: default exclusion of archived lists and the required OAuth scope (newsletter:read). Since output schema exists, it needn't explain returns. Adequate with 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?

Single sentence, front-loaded with purpose and default behavior, then auth scope and a pointer to a related tool. No wasted words.

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?

Annotations cover safety and output schema covers returns, so the description has a lighter burden. However, with 0% schema coverage on four parameters, the description leaves significant gaps (limit, cursor semantics), making it incomplete for correct invocation.

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 0%, so all four parameters (limit, cursor, project_id, include_archived) lack schema-level documentation. The description mentions include_archived indirectly ('archived lists are excluded by default') but provides no meaning for limit, cursor, or project_id. It doesn't compensate for the coverage gap.

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 (List) and resource (newsletter audiences/lists), clarifies scope ('for signup forms') and default behavior ('archived lists are excluded by default'). Distinguishable from siblings like list_newsletter_custom_fields.

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?

Clearly indicates this is for retrieving newsletter audiences and explicitly points to get_newsletter_schema for document/filter/field definitions, routing the agent properly. It doesn't state explicit exclusions beyond archived lists, but the sibling pointer provides clear usage guidance.

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