Katzilla MCP

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true, covering safety and idempotency. The description adds valuable context beyond annotations: it specifies the API source (Frankfurter), update frequency (monthly), and details the return format (Katzilla envelope with quality scores and citation). This enhances behavioral understanding without contradicting 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 efficiently structured into two sentences: the first states the purpose and usage, and the second details the source, update frequency, and return format. Every sentence adds essential information without redundancy, making it front-loaded and concise.

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 (currency exchange rates), rich annotations (read-only, idempotent, open-world), 100% schema coverage, and the presence of an output schema, the description is complete. It covers the purpose, usage, source, update frequency, and return format, providing all necessary context for an AI agent to use the tool effectively.

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 both parameters ('base' and 'symbols') well-documented in the schema. The description mentions 'optional symbol filtering' and 'any base currency,' which aligns with but does not add significant meaning beyond the schema. Since the schema does the heavy lifting, the baseline score of 3 is appropriate.

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: 'Latest currency exchange rates via Frankfurter API. Get rates for any base currency with optional symbol filtering.' It specifies the verb ('get'), resource ('currency exchange rates'), and distinguishes it from sibling tools like 'economic__exchange-rates' by mentioning the specific API source (Frankfurter) and the Katzilla envelope return format.

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 usage: 'Get rates for any base currency with optional symbol filtering' and notes the source and update frequency ('Source: Frankfurter (European Central Bank) (Free / Open), updates monthly'). However, it does not explicitly state when to use this tool versus alternatives like 'economic__exchange-rates' or other sibling tools, which prevents a score of 5.

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