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

With no annotations provided, the description carries the full burden of behavioral disclosure, but it only states the action without mentioning any side effects, authentication requirements, rate limits, or return format. It fails to convey that this is likely a read-only operation or that the npub parameter is tied to credit billing, which is only revealed in the schema.

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 concise sentence that is front-loaded with the primary verb and object. It avoids unnecessary words, which is good for conciseness, though it may be too sparse to provide full context. No structural issues.

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?

Despite having an output schema, the description lacks sufficient context for a tool with two parameters and no annotations. It does not mention the billing requirement, the purpose of the parameters, or any behavioral details. For a tool that lists brains, the description is minimal but functional; however, the lack of additional context makes it incomplete for agents that need to know how to invoke it 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?

The description adds no parameter information beyond the input schema. Schema description coverage is only 50% (npub has a description, dpop_token does not), so the description should compensate, but it does not. The dpop_token parameter remains completely unexplained, and the tool description does not clarify the billing context of npub.

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 'List available brains.' clearly states the action (list) and the resource (brains), making it easy to understand the tool's basic function. However, it does not distinguish this from sibling tools like brain_get_brain or specify the scope of 'available brains' (e.g., user's own vs all accessible), so it lacks sibling differentiation.

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?

There is no guidance on when to use this tool versus alternatives. With many sibling tools for brain-related operations, the description gives no indication of prerequisites, context, or exclusions, leaving the agent without sufficient information to choose it confidently.

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