Fabits MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions that OTP is sent to a phone number and must be called first, but lacks details on rate limits, error handling, session state implications, or what happens if called repeatedly. For a login-related tool, this is a significant gap in transparency.

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 front-loaded and concise, consisting of two sentences that efficiently convey the tool's role in the login flow without unnecessary details. Every sentence earns its place by stating the action and prerequisite step.

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's complexity (login step with 2 parameters), no annotations, and no output schema, the description is minimally adequate. It covers the basic purpose and sequence but lacks details on behavioral aspects, error cases, or return values, which are important for a login tool in a financial 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%, so the schema already documents both parameters (user_id and phone_number) with their purposes and formats. The description does not add any additional meaning beyond what the schema provides, such as explaining the relationship between user_id and phone_number or usage nuances, resulting in a baseline score of 3.

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 as 'Step 1 of login: Request OTP to be sent to phone number,' specifying the action (request OTP) and resource (phone number). It distinguishes itself from sibling tools like 'fabits_verify_otp' by indicating this is the first step in a login flow, though it could be more explicit about the login context (e.g., for financial services).

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 clear context on when to use this tool: as the first step in login before verifying OTP. It implicitly distinguishes from 'fabits_verify_otp' by sequence, but does not explicitly mention alternatives or exclusions, such as when not to use it (e.g., if already logged in).

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