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

Annotations already declare a non-read-only, non-destructive, non-idempotent write in a closed world, so the description's job is to add context, and it does: 'Test mode only: no settlement' plus the mode semantics (wallet accepts Kivel test wallet tokens, permissive validates structure only). It omits what happens to the paywall when ttlSeconds elapses or what 'response' controls, leaving some behavioral surface unexplained.

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?

Four tight sentences with no filler, and the core purpose plus the test-mode caveat are front-loaded. The routing sentences are dense but each earns its place.

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 mutation tool with a nested response object, two required params, and zero schema descriptions, the behavioral and routing picture is good but the parameter picture is thin. An agent knows what the tool does and how to follow up, yet not how to shape amount, ttlSeconds, or response 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 description coverage is 0% across six parameters, so the description must carry the load, and it only explains the meaning of the modes values. Required fields name and amount are never characterized — no units, currency, or format — and ttlSeconds, response (a nested object), and description are entirely unaddressed.

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 first sentence states a specific verb and resource — 'Create a public mock x402 v1 paywall' — which is materially distinct from siblings like create_mock_api or create_test_checkout. The qualification 'Test mode only: no settlement' immediately narrows the scope further.

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 description routes the agent explicitly: use inspect_mock_api to inspect requests, and resource_request with kind test-paywalls to configure or delete. That is clear alternative guidance for the post-creation lifecycle, though it never contrasts this with create_test_checkout or create_mock_api for agents choosing among creation tools.

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