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. It discloses that the token is validated, cached for subsequent calls, and never echoed. This gives useful operational transparency about session state and privacy, though it doesn't mention error handling or what happens on invalid tokens.

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 three sentences, each adding distinct value: purpose and alternative, validation and caching, and privacy. It is front-loaded with the main action and contains 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?

For a simple two-parameter tool with an output schema, the description covers the core aspect (session-scoped token usage), validation, caching, and privacy. It lacks some context around base_url and prerequisites, but overall it is sufficiently complete for the tool's complexity.

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 0%, so the description must compensate. It explains the 'token' parameter's format (brainkb_pat_...) and role, but the optional 'base_url' parameter is left entirely unexplained. This is a partial compensation, leaving one parameter without semantic guidance.

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 clearly states the tool's action: using a Personal Access Token for the current session, with the specific token prefix 'brainkb_pat_...'. It also distinguishes itself from the alternative of setting BRAINKB_TOKEN in config, making its unique role unambiguous even among many sibling auth-related tools.

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 explicitly frames the tool as an alternative to setting BRAINKB_TOKEN in the config, providing clear context for when to use it. However, it doesn't explicitly state when not to use it or name a sibling tool as a fallback, so it misses the full exclusionary guidance that would warrant a 5.

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