Katzilla MCP

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

Annotations already indicate read-only, non-destructive, idempotent, and open-world behavior. The description adds valuable context beyond annotations: it specifies the data source (iRail API with CC0 1.0 license), update frequency (daily), and details about the return format (Katzilla envelope with quality scores and citation including SHA-256 hash). This enhances transparency about data provenance and output structure, though it doesn't cover rate limits or error handling.

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 efficiently structured in two sentences: the first states the purpose and source, the second details the return format. Every element (e.g., API source, update frequency, output structure) adds value without redundancy. It is front-loaded with core functionality and appropriately sized.

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 moderate complexity (2 parameters, 100% schema coverage, annotations, and an output schema), the description is complete. It covers purpose, source, update frequency, and output format, compensating for any gaps. With annotations and output schema handling safety and return values, no additional details are needed for effective use.

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 clear parameter descriptions for 'from' and 'to'. The description adds minimal parameter semantics beyond the schema, only implying that parameters are used for connections (not for station lists). It doesn't clarify syntax, examples beyond the schema, or how parameters interact (e.g., both optional for station list). Baseline 3 is appropriate as the schema does the heavy lifting.

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 explicitly states the tool's purpose: 'Get Belgian railway (NMBS/SNCB) station list or connections between stations using the iRail API.' It specifies the exact action (get), resource (station list or connections), and scope (Belgian railway via iRail API). This clearly distinguishes it from sibling transport tools like 'transport__bc-ferries' or 'transport__swiss-transport' which cover different transport modes or regions.

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 for when to use this tool: for Belgian railway data (station lists or connections). However, it does not explicitly mention when not to use it or name specific alternatives among siblings (e.g., for non-Belgian transport data). The guidance is sufficient for basic usage but lacks explicit exclusions or comparisons.

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