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

The description goes far beyond the annotations, revealing key behaviors: the credential is short-lived and bound to exact payment details, verification is offline via a specific endpoint, unpaid calls return a challenge, conflicting carriers fail closed, requests are never charged if malformed, and api_key uses sandbox credits. This is rich, non-obvious context that helps an agent understand side effects and failure modes.

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?

Despite being long, every sentence delivers actionable information: timing, return value, verification endpoint, transport mapping, retry protocol, failure semantics, billing behavior, and alternative. The structure is front-loaded with the most critical call-to-action, followed by supporting details. No filler or redundancy.

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 complex tool with 6 parameters, nested objects, and an output schema, the description fully covers the operational workflow, security model, and alternatives. It explains what the tool returns, how to verify, how to retry, and what happens on failure. The output schema exists, so the description needn't document return values. This is a complete and self-sufficient description.

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 low (17%), so the description compensates. It explains the core parameter 'payment' is bound to scheme, CAIP-2 network, asset, amount, payee, and resource URL. It clarifies 'x402_payment' as an alternative carrier for adapters, and notes 'api_key' uses sandbox credits. However, 'capability' and 'ttl_seconds' are not elaborated beyond their names, leaving minor gaps.

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 states the tool's purpose: 'Call this immediately BEFORE signing an x402 payment envelope.' It specifies that it returns an authorization credential, distinguishing it from sibling envelope tools like guild_envelope_issue or guild_envelope_verify. The verb 'Authorize' in the title and the detailed behavior make it unambiguous.

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?

Explicit when-to-use: 'Call this immediately BEFORE signing.' It names an alternative: 'The free identity-only alternative is GET /wallet-binding/resolve.' It also identifies this as the native MCP transport for an existing HTTP product, giving clear context for integration. No competing MCP sibling is mentioned, but the timing and alternative are explicit.

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