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

Beyond the annotations (readOnlyHint=false, idempotentHint=true), the description discloses important behavioral traits: the login happens in a browser, the result is an access token, and there are two distinct persistence modes (permanent non-expiring vs session-only). It also notes that passing no arguments returns a link. This adds meaningful context about the workflow and side effects, though it does not mention what happens to existing sessions or token storage.

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 compact and front-loaded, starting with the core purpose, then providing two usage alternatives. Every sentence adds information: purpose, recommended config approach, and session-only fallback with parameter usage. No fluff or repetition, and the structure flows logically from permanent to session-based authentication.

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?

Given the tool's complexity (two auth modes, browser interaction, optional token parameter), the description covers the essential scenarios and how to invoke them. It even notes the no-argument behavior. However, with no output schema and no mention of return values beyond 'get the link', the agent may not know what the response contains (e.g., a URL vs confirmation). Still, for a simple auth tool, the description is largely adequate.

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?

With 0% schema description coverage, the description compensates well. It explains the 'token' parameter's semantics: a JWT to be pasted for session-only login, and that omitting the token triggers a link generation flow. It also clarifies the usage context ('after the user pastes'), which gives the agent concrete invocation guidance. The only gap is that it doesn't specify the exact expected input format beyond 'jwt' or any validation details.

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 purpose: logging in and obtaining an access token for MCP.AI. It specifies the concrete actions (log in in the browser, copy the access token) and distinguishes itself from siblings like 'connect' by focusing on authentication/token acquisition. The verb 'log in' and resource 'access token' make the function unambiguous.

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 provides clear usage context: it explains two distinct invocation modes (permanent via config header, session-only via token argument) and explicitly recommends the config option as 'Best'. It also clarifies when to call with no arguments ('to get the link'). However, it does not explicitly contrast with sibling tools like 'connect', so the when-not-to-use guidance is implicit rather than explicit.

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