setup_auth

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

No annotations are provided, so the description carries the full burden. It discloses that the key is validated before saving and a wrong key is never stored, which is important behavioral context. It also provides a specific URL for key generation. It does not mention what happens on success (e.g., confirmation), but the core behavior is transparent.

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 only two sentences, with the purpose front-loaded, followed by validation behavior and user instruction. Every sentence adds value, and there is 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 single-parameter setup tool, the description covers the purpose, the input source, and the validation side effect. It does not explicitly describe the output (none defined) or error scenarios, but the core usage is fully captured. Sibling tools exist for status checks, but that does not detract from completeness here.

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 coverage is 0%, so the description must compensate for the undocumented api_key parameter. It does: it defines the key as the Splitwise API key, explains how to obtain it, and notes that validation occurs. This goes well beyond the bare schema field name.

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 ('Configure or replace') and a clear resource ('Splitwise API key'). It also states the validation action, making the tool's purpose unmistakable. It is clearly distinct from siblings like get_auth_status and logout, which deal with status and session termination.

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 makes it clear this tool is used when the user needs to set up or replace the API key, and instructs the agent to ask the user for a key. It gives clear context but does not explicitly mention when NOT to use it or name alternative tools, so it falls just short of a 5.

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