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

Annotations only indicate read-only, idempotent, open-world, and non-destructive. The description adds important behavior beyond those: page size cap, possible empty page with continuation cursor, opaque transport-bound cursor, and authentication guidance to keep the lease bearer off tool arguments. No contradiction 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?

Two tightly written sentences with no filler. The core listing/wait behavior and pagination semantics come first, followed by the critical authentication constraint. Every sentence adds value.

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?

Given the output schema, annotations, and the provided cursor/wait constraints, the description covers the key operational details: page cap, cursor continuation, bounded wait, empty-page possibility, and transport-level auth. Nothing essential is missing for a caller to use the tool correctly.

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 the description shoulders the semantic burden. It effectively explains the roles of inbox_id, after, and wait_seconds even without naming them directly: active inbox, opaque cursor, and up-to-30-second wait. The schema itself adds cursor constraints and bounds, and the description adds meaningful behavioral context on top.

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 states a specific action: return or wait for normalized message summaries for an active inbox, with concrete bounds ('at most 50', 'after an opaque inbox-bound cursor'). It clearly distinguishes this list/wait operation from sibling tools like read, delete, or attachment retrieval.

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 clear context: this is for listing or waiting on inbound messages in an active inbox, using a cursor and optional bounded wait. It does not explicitly name alternatives or state when not to use it, but the behavior is unambiguous enough for an agent to select it appropriately.

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