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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), and the description goes further by disclosing a hard gating condition (model access must be enabled) and a prompt-injection handling policy for returned fragments. It also flags that results are private user data that should not be relayed without consent — context an agent cannot derive from any structured field.

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 sentences, each carrying distinct load: what it searches, when it works, and how to treat the output. The corpus definition is front-loaded and there is no filler or repetition of the title.

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?

With an output schema present and full parameter coverage, the description need not explain return values, and the addition of the model-access prerequisite and untrusted-content handling closes the two gaps the structured data leaves open. A minor omission is what the agent should do if model access is not yet enabled, but the tool is otherwise adequately specified.

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 100%, so kinds, limit, and query are already fully documented in the schema. The description adds only the general "by meaning" framing, which reinforces that query is natural language but does not add format, syntax, or default details beyond what the schema states.

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?

"Searches the user's Brain by meaning: their own documents and notes" gives a specific verb (semantic search), a specific corpus (the user's private Brain content), and a mode (by meaning, not keyword). It does not explicitly contrast with the similarly-named sibling semantichub_search_articles, so the agent must infer that the Brain is the private store rather than the public articles index.

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?

It supplies a real prerequisite (model access must be enabled by the user in the panel), which tells the agent when this call will fail. It gives no guidance on when to prefer this over semantichub_search_articles or the api_search sibling, so the sibling choice is only implied by the corpus wording.

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