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

With no annotations, the description carries the full burden and does disclose a genuinely important trait: the key cannot be recovered and is the only credential for watches, which tells the agent this is an irreversible secret issuance. It omits whether the key value is returned in the response and any rate or plan limitations on key creation.

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?

Three short sentences with the core action front-loaded and the critical warning placed immediately after. The standalone 'Free.' at the end duplicates 'free-plan' and is the one sentence that does not earn 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 creation tool with no output schema, the most important missing detail is whether the generated key is returned in the response body — the description says 'Save it' but never says where the agent will receive it. Combined with the absent usage prerequisites, the definition is adequate but leaves a real operational gap.

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 takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a param-less schema applies. The mention of 'free-plan' usefully explains why no plan argument exists.

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 ('Create a new free-plan API key'), which is clearly distinguishable from the watch-oriented siblings (add_watch, list_watches, etc.). The trailing 'Free.' restates the plan tier already given in the first sentence, adding slight redundancy rather than new precision.

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?

Usage is only implied: the reference to 'your watches' hints that this credential is needed before creating or managing watches, but the description never says when to call it versus other tools or whether it is required setup. There are no explicit exclusions or prerequisites stated.

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