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

With no annotations provided, the description carries the full burden, and it delivers: it explicitly states the tool does not block/wait and explains why a synchronous MCP call can't sit through a multi-minute browser approval. It also discloses the return values (user_code, verification URL, device_code) and the human-in-the-loop requirement, which is critical behavioral context beyond the schema.

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?

The description is dense but every sentence earns its place: it states the action, the required human steps, the client_id guidance, the follow-up call, and the non-blocking behavior. It is front-loaded with the core purpose and flows naturally into usage details without repetition or filler.

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 single-parameter tool with no output schema, the description is complete: it explains the flow, the human interaction, the follow-up call, and the non-blocking constraint. An agent has everything needed to invoke it correctly and know what to do with the result, even without an output schema.

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 coverage is 100% and the single parameter is already well documented in the schema. The description adds value by explaining why the client_id matters (so the approval screen shows the client's name) and when to omit it, which goes beyond the schema's default-null note. A 4 is appropriate because the description enriches the parameter's purpose even though the schema already covers its syntax.

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 verb ('Start a device-code sign-in'), names the RFC 8628 shape, and clearly distinguishes this from the sibling device_claim by explaining that this tool initiates the flow while device_claim polls for the result. It also names register_client as a related sibling, so an agent can tell them apart.

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 explicit when-to-use guidance: pass the client_id from register_client if it was called, and call device_claim afterward with the returned device_code, polling per its interval. It also tells the agent to show both the user_code and verification URL to the human, which is essential usage context. No exclusions are needed because the tool's role in the flow is fully specified.

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