What needs me?

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

With no annotations, the description must carry the full burden of disclosing behavior. It explains the content and payload (requestIds), but does not explicitly state whether this is a read-only operation or any other safety/side-effect characteristics. For an inbox-like tool, this is a notable omission.

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 sentences, front-loaded with the core concept 'Cross-thread inbox', and no wasted words. Every sentence serves a purpose: defining the tool and linking to related tools.

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 0-parameter tool with no output schema, the description does a good job of explaining what is returned and how to use it with sibling tools. It could be more explicit about the response format or grouping, but it's sufficient for an agent to invoke it and inspect the response.

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?

The tool has zero parameters, so the baseline is 4. The description adds value by mentioning requestIds for sibling tools, but this isn't about the tool's own parameters. Thus it meets the baseline without needing further clarification.

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 clearly identifies the tool as a 'Cross-thread inbox' listing every thread blocked on the human, with specific item types (approvals, questions, plans, errored sessions). This distinguishes it from siblings like list_threads or get_thread, which focus on threads generally or individually.

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 provides clear context for when to use it—when there are pending actions requiring human attention—and even mentions the requestIds needed by respond_to_approval / respond_to_user_input, showing a usage chain. However, it doesn't explicitly say when not to use it or contrast with alternatives.

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