auth_login

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

The description discloses the full flow: returns a verification URL and code, the server automatically receives credentials, and all API calls become linked to the user's account (tier, credits, rate limits). This goes well beyond the annotations, which only state idempotentHint=true and destructiveHint=false. No contradiction with annotations.

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, front-loaded with the primary purpose, then providing essential behavioral details and the explicit usage condition. Every sentence earns its place with no redundancy or fluff.

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 no input parameters and no output schema, the description is complete: it explains what action occurs, what the user sees (verification URL/code), what happens next (automatic credential receipt), and the prerequisite conditions. It fully answers likely agent questions about whether to invoke this tool.

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?

The tool has zero parameters, so the schema is fully self-explanatory. The description reinforces that no parameters are needed by describing the flow as automatic. Baseline 4 is appropriate for a parameterless tool.

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 uses a specific verb ('Start the device authorization flow') and a clear resource ('connect this MCP server to your OpenEphemeris account'). It fully distinguishes itself from sibling auth tools like auth_logout and auth_status by describing the login/connect action rather than logout or status checking.

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?

Explicitly states when the tool is needed: 'Only needed if no OPENEPHEMERIS_API_KEY env var is set and no cached credentials exist.' This gives the agent a clear decision rule. It also provides context about the free tier, which helps decide if this is appropriate to offer to users.

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