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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds important behavioral context beyond those annotations by stating that the output contains masked keys and warning against revealing full credentials, which the annotations do not convey.

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?

The description is a single compact sentence that front-loads the core purpose ('List masked merchant API keys') and adds one essential security caveat. Every word earns its place; there is no filler or repetition.

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?

Given the tool's simplicity, zero parameters, existing output schema, and annotations that cover safety and idempotency, the description is complete. Nothing an agent needs to call this tool correctly is missing; the masked-keys warning is the only critical non-schema behavior and it is present.

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 zero parameters, there is no parameter documentation burden. The description appropriately explains the scope of the operation without needing to elaborate on inputs, so the baseline of 4 is appropriate.

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 uses a specific verb ('List'), names the exact resource ('merchant API keys'), and adds a distinguishing qualifier ('masked') that sets it apart from the other list/get tools. This is unambiguous and directly actionable for an agent.

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 implies the tool is for retrieving masked merchant API keys, but it does not explicitly state when to use it versus alternatives or list any exclusion criteria. For a zero-parameter simple list tool, this is minimally adequate but leaves the when-to-use decision mostly implicit.

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