Fabits MCP Server

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 the tool's purpose (refreshing tokens) and trigger condition (401/403 errors), but lacks details on behavioral traits like rate limits, side effects (e.g., invalidating old tokens), error handling beyond 401/403, or response format. The description adds basic context but misses deeper operational insights.

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 two sentences with zero waste: the first states the purpose, and the second provides usage guidelines. It is front-loaded with essential information and appropriately sized for a single-parameter tool with a clear, focused function.

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 no annotations and no output schema, the description is moderately complete. It covers the tool's purpose and usage trigger effectively, but for a token refresh operation—which involves authentication state changes—it lacks details on expected outcomes (e.g., new token format), error scenarios beyond 401/403, or dependencies on other tools. This leaves gaps in operational context.

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%, with the single parameter 'user_id' fully documented in the schema. The description does not add any parameter-specific details beyond what the schema provides, such as explaining why 'user_id' is needed for token refresh. Baseline 3 is appropriate as the schema handles parameter documentation adequately.

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 specific action ('Refresh expired access token') and resource ('using the stored refresh token'), distinguishing it from siblings that handle investments, portfolio queries, or authentication flows like OTP verification. It directly addresses token renewal, a distinct operational need.

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?

It explicitly states when to use this tool ('when you get 401/403 errors due to token expiration'), providing clear context for invocation. This guidance helps differentiate it from other authentication-related tools like 'fabits_verify_otp' or 'fabits_request_otp', which handle initial login rather than token refresh.

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