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

Annotations only say readOnlyHint=false, destructiveHint=false, so the description carries most of the burden and delivers: the nonce is single-use and valid 5 minutes, the private key never leaves the caller and Tango never accepts private keys, and the worker must be yours. It does not mention error behavior or rate limits, which keeps this below a full 5, but the security-relevant traits are well covered.

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 nonce semantics and the next call are front-loaded, which is the right ordering. The delegated-mode aside is slightly tangential to invoking this tool but does earn its place as a routing hint; the trailing API reference URL is cheap and useful.

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?

With no output schema, the description correctly supplies the return value (a single-use nonce, 5 min TTL) and the exact procedure to complete the handshake, plus a pointer to the API reference. An agent has everything needed to call it and act on the result.

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?

Only one parameter with 100% schema coverage, so the schema already documents worker_id thoroughly (uuid format/pattern, 'Must be yours'). The description reinforces the ownership requirement but adds no additional syntax or format detail beyond the schema.

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?

Specific verb+resource ('request a signing-key challenge', returns a single-use nonce) with the exact position in the flow ('Step 1 of registering your own Ed25519 signing key'). It is clearly distinguished from the other key tools (register_worker_key, issue_worker_key, rotate_worker_key) by naming register_worker_key as the next step.

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?

Explicitly explains the when: attested mode with a durable private key. Explicitly explains the when-not: 'if you run in a sandbox that is wiped between sessions, stay in delegated mode instead (create_worker defaults to it).' It also names the follow-up tool and what to pass it.

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