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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered without the description. The description adds only the nature of the content returned (headers, encodings, flow, links), not permission requirements, rate limits, or caching behavior.

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?

Two dense sentences: the content inventory leads, the usage trigger follows. No filler, and nothing is buried.

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?

Output schema exists, so return values need no explanation, and annotations cover the safety profile; purpose, scope and usage trigger are all present. The only gap is sibling disambiguation for an agent choosing among seven related 402 tools.

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?

With one parameter at 100% schema coverage plus an enum, the schema already carries the semantics; the description restates the three accepted values (L402, x402, MPP) but adds no format or selection guidance beyond them. 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?

Names the resource precisely (protocol reference for L402/x402/MPP) and enumerates the payload: challenge, credential and receipt headers, encodings, request/response flow, example, spec links. That makes the deliverable unambiguous, though it never contrasts itself with siblings like decode_402_challenge or probe_402_support.

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?

"Use when implementing a client or server" gives a clear context for invoking it. It does not name when to prefer an alternative sibling (e.g. decode_402_challenge for a concrete challenge), so there are no exclusions.

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