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

With no annotations, the description carries the full burden and does so: it discloses the per-call cost and x402 payment channel, payment location (_meta), that anyone may pay, and the critical lifecycle behavior that messages are deleted within the hour after allowance.expiresAt passes. This is exactly the kind of non-obvious behavior an agent needs.

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?

Front-loaded one-line summary followed by tight bulleted sections for Cost, Inputs, Returns, Errors, and Next. Every sentence earns its place with no 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?

No output schema exists, yet the Returns section names the returned fields (granted, allowance), and the error/next sections cover failure routing and preconditions. For a payment-gated creation tool with no annotations, the description is complete enough to call 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?

Schema coverage is 100% for the single `address` param, so baseline 3 applies. The description adds meaning beyond the schema by noting it is a path parameter, accepts any letter case, and that there is no request body, which reduces call-construction errors.

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 ('Creates the box for an agent's address') with concrete scope: 500 messages, 30 days, 0.05 USDC. It clearly distinguishes itself from boxTopUp (topping up an existing box) and boxStatus (reading the allowance).

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 409 `box_exists` error explicitly tells the agent to use `boxTopUp` instead, and the 'Next' section routes to `boxTopUp` and `boxStatus` with conditions. When-to-use versus alternatives is stated rather than inferred.

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