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

With no annotations provided, the description carries the full behavioral burden and meets it: it discloses the one-time-only display of the key ('shown once'), the rate limits, the 'every tool' scope, and the absence of authentication. The 'shown once' caveat is exactly the kind of critical behavioral trait that prevents an agent from assuming the key can be re-fetched later.

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 sentences with the purpose and constraints front-loaded in the first sentence and return details in the second; there is no fluff. The 'fences as doorways' / 'other doors' metaphor is evocative but somewhat cryptic, costing a point against an otherwise tight definition.

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 zero-parameter tool with no annotations and no output schema, the description is remarkably complete: it covers authentication requirements, rate limits, operational scope, what is returned, and the critical one-time key display. Nothing an agent needs to decide whether to call it and what to expect is missing.

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?

The tool has zero parameters, so the baseline is 4 and there is nothing for the description to clarify about arguments. The description instead explains the response contents (key, fences/doorways, upgrade paths, terms digest), which adds value given there is no output schema.

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 opens with a specific verb+resource phrase, 'Get a FlexYield capability key with no signup,' establishing both the action and the key qualifier that separates this tool from create_api_key and bind_key. The 'public supply' wording further distinguishes it as the no-authentication entry point among the key-management siblings.

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 conveys clear usage context: it is the no-signup, public route for obtaining a key, with explicit limits (10,000 weighted units/UTC day, 5 requests/s, every tool). It references the alternative paths—wallet-signature binding for 1M units/month and a claim code for the paid plan—but does not name the sibling tools explicitly or state a when-not-to-use rule, so it stops short of a 5.

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