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

No annotations exist, so the description must carry full weight. It discloses the npub requirement for credit billing, which is a meaningful behavioral trait. However, it omits other important aspects like partial update semantics, validation, and potential side effects.

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 sentence that front-loads the action and adds the critical billing requirement. It contains no filler and is immediately scannable.

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 9-parameter mutation tool with no annotations, the description is quite minimal. The schema covers most parameters and an output schema exists, but the description still lacks explicit guidance on update behavior (e.g., partial vs. full replacement) and use context, making it only partially complete.

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?

Schema description coverage is 89%, so the schema already documents most parameters. The description adds no additional parameter-level meaning, but it does not contradict the schema either. Baseline 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 'Update link properties' is a specific verb+resource statement that clearly distinguishes this tool from siblings like brain_create_link, brain_get_link, and brain_delete_link. It immediately conveys the action and target.

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 usage for modifying existing links, but it does not explicitly state when to use this tool versus alternatives, nor does it mention exclusions. The npub requirement is a practical hint but not a full usage guideline.

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