start_authentication

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

Annotations already indicate readOnlyHint=false, openWorldHint=true, idempotentHint=true, and destructiveHint=false. The description adds behavioral context beyond annotations: it returns a short code and URL, and requires user interaction (opening the URL and entering the code). It also enumerates the endpoints that require authentication, which is useful context. Since annotations cover the safety profile, the description's added flow details earn a 4.

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 exceptionally concise: two sentences plus a list of endpoints. The purpose is front-loaded ('Begin signing in to Trakt'), followed by return value and instructions, then the scope of usage. Every sentence earns its place, and the structure is clear and 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?

Given the tool has zero parameters and an output schema (which presumably describes the return values), the description covers all necessary context: what it does, what it returns, what to do next, and when it's needed. It also lists the affected endpoints, leaving no ambiguity about when to invoke it. The description is complete for an agent to use it correctly.

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?

There are no parameters, so schema coverage is trivially 100%. The description doesn't need to explain any parameters, and it doesn't. The baseline for no parameters is 4, which is appropriate here since the description adds no parameter-specific semantics (and none are needed).

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: 'Begin signing in to Trakt.' It specifies the action (begin signing in) and the resource (Trakt), and differentiates from siblings like finish_authentication and clear_authentication by describing the initial step of the authentication flow. It also explains what it returns (a short code and a URL) and what to do with them, making its purpose 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 explicit guidance on when to use this tool: 'Only needed for the endpoints that act on an account: sync, users/me, checkin, scrobble, recommendations and lists you own.' It also instructs the next step ('then call finish_authentication'), giving a clear usage context. It implies that for non-account endpoints, this tool is not required, which is sufficient differentiation.

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