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

With no annotations, the description must bear the burden of behavioral disclosure. It does add the non-obvious detail that npub is required for credit billing, which implies a metered operation. However, it lacks other important behaviors like whether the file must exist locally, whether the operation is reversible, or any rate limits.

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 two sentences long, front-loaded with the core action, and contains no fluff. Every word contributes value.

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 and decent parameter coverage, the description is too sparse for a 6-parameter tool with no annotations. It omits context about default brain behavior, file requirements, and the exact nature of the attachment operation, leaving the agent with significant gaps.

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 schema already covers 83% of parameters with descriptions, including npub's billing purpose. The description reinforces the npub requirement but adds no new parameter semantics beyond what the schema provides, so a baseline score of 3 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 states a specific verb and resource: 'Add a file attachment to a thought.' This clearly distinguishes it from sibling tools like brain_add_url_attachment or brain_delete_attachment, as it focuses on attaching a local file to a thought.

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?

No guidance is provided on when to use this tool versus alternatives. The close sibling brain_add_url_attachment is not mentioned, and there is no explanation of prerequisites or typical scenarios beyond the implicit need for a file attachment.

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