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

With annotations only declaring readOnlyHint=false and idempotentHint=false, the description carries substantial extra load: the full human-in-the-loop handoff via approval_url, the authentication/identity/payment steps, 'no refunds after activation', the commercial-use restriction, and the mandate_unavailable outcome. This is exactly the behavioral context annotations cannot express.

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?

One dense paragraph that front-loads the action, the return value and the human steps before the caveats. Every sentence conveys something actionable, though the run-on construction around authentication and payment could be split for faster scanning.

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 4-parameter mutation tool with a nested mandate object and an output schema, the description supplies the preconditions, the human approval flow, the error vocabulary (taken, not_listed, mandate_unavailable) and the refund/activation policy. Nothing an agent needs to invoke it correctly appears to be missing.

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 100%, so host, client, term_months and the mandate object are already documented, including the term enum and per-month pricing relationship. The description repeats term options and mandate unavailability rather than adding new meaning, so baseline 3 applies.

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?

States a specific verb and resource ('Starts renting one listed name for a term') and names the observable outcome (returns an approval_url for the human to open). That distinguishes it cleanly from siblings like search_names, get_rent_status and how_to_rent without needing their schemas.

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?

'Call it once the user has chosen the name and term' gives an explicit precondition, and the mandate sentence effectively excludes a mode ('not available yet'). It also tells the agent what happens on failure (taken / not_listed with listed alternatives), though it never routes the agent to how_to_rent or get_lease_terms by name.

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