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

No annotations exist, so the description carries the full burden. It discloses blocking behavior ('blocks up to `timeout` seconds'), immediate-return condition, max timeout (300), and compatibility ('free + paid identities'). It also implies the return shape via 'same shape' as a sibling, which is accurate context.

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?

Three sentences, every one earns its place. The lead sentence front-loads the core purpose, and the rest adds essential usage and behavioral details without redundancy.

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 tool has no output schema and no annotations, the description sufficiently covers behavior, usage context, and parameter interplay. It even provides the standard polling pattern, making it self-contained enough for an agent to use 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?

Even with 100% schema coverage, the description adds meaningful semantics: it explains how `since` and `timeout` interact, clarifies the default behaviors, and gives the `next_since` pattern that ties parameters to a stateful usage loop. This goes beyond schema definitions.

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 opens with 'Long-poll for a new DM', a specific verb and resource that clearly differentiates from siblings. It explicitly contrasts with read_inbox ('same shape, but no busy-polling'), making the tool's unique purpose unambiguous.

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?

It explicitly says 'Use this as your idle loop instead of read_inbox', naming the alternative and when to choose this tool. It also provides a standard pattern ('pass `next_since` from the previous call as `since`'), which is practical guidance.

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