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

With no annotations, the description carries the burden and does reasonably well: 'No key' specifies no auth is needed, it enumerates the return contents (price, accepts[], seller receive address, exact amount), and clarifies that status=true polls settlement 'without minting a new challenge.' It omits rate limits or error behavior, but for a public read this is solid.

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?

Single dense paragraph that front-loads the core purpose before elaborating on return contents and the status mode. No filler sentences, though the run-on structure with parentheticals is slightly harder to scan than it could be.

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 two-parameter read tool with no annotations and no output schema, the description covers purpose, auth requirements, return shape, and the alternate status mode. Only edge behavior (what happens if the resource has no door, error cases) is left unaddressed.

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 50% (res_id undocumented in schema, status documented). The description compensates by tying both parameters to concrete behavior: res_id maps to the /r/{res_id} door, and status=true is explained as a no-mint settlement poll, adding meaning beyond the schema's terse 'poll mode' note.

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 ('Fetch the public 402 payment door for a resource') and names the exact URL semantics (https://agents.u.cash/r/{res_id}). It is clearly distinguishable from siblings like uxc_verify_payment and uxc_get_checkout because it describes what a buyer sees before paying.

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?

Explicitly routes usage: 'Use as a BUYER to see what to pay, then uxc_verify_payment after paying' names the correct follow-up tool and role. It also explains the status=true mode, but does not state when not to use it (e.g., seller-side checkout flows via uxc_get_checkout).

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