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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it opens a browser page, requires the user to copy a token, and notes token expiration (~1 hour) and the need to re-login on auth errors. This goes beyond the annotations and helps the agent manage the auth lifecycle. Minor gap: it doesn't state what happens if the token is invalid or expired, but the auth-error guidance covers that.

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 earning its place: purpose, the login flow, and token expiration/re-login guidance. It's front-loaded with the main purpose and then provides necessary operational details. No fluff or repetition of schema content.

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 one-parameter auth tool with no output schema, the description covers the essential flow: how to initiate login, how to provide the token, and what to do on expiry. It doesn't describe the output/return value (e.g., what a successful login returns), but since there's no output schema and the tool is primarily a state-changing auth step, this is a minor gap. The description is complete enough for an agent to invoke 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?

Schema description coverage is 100%, so the schema already documents the token parameter. The description adds meaning by explaining the two-step usage: leave empty on first call to get the login URL, then paste the token. This is essential context that the schema alone doesn't provide, so the description compensates well. Slight deduction because the description doesn't specify the token format or what 'empty' means exactly (e.g., empty string vs omitted), but the schema's 'Leave empty' is clear enough.

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: signing in to a Rhylthyme account to enable listing/saving schedules and importing from external sources. It uses a specific verb ('Sign in') and resource ('Rhylthyme account'), and the title 'Connect Rhylthyme account' aligns well. It distinguishes itself from siblings by focusing on authentication, which none of the sibling tools do.

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 when-to-use guidance: use it first to authenticate, and call it again if a later call reports an auth error because tokens expire after about an hour. It also explains the two-step flow (leave token empty first, then provide token). This is clear and actionable, though it doesn't explicitly name alternatives—but there are no real alternatives for login among siblings.

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