Frankfurter MCP

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

Annotations indicate readOnlyHint=true and openWorldHint=true, covering safety and data scope. The description adds valuable behavioral context: it explains fallback behavior ('closest date before' if unavailable), clarifies parameter requirements ('Either a specific date, a start date, or a date range must be provided'), and notes default behavior for symbols. No contradiction with 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 well-structured and front-loaded with the core purpose. Each of the four sentences adds distinct value: purpose, fallback behavior, parameter requirements, and symbols filtering. There is no wasted text, and it efficiently covers key aspects without redundancy.

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 (historical data with fallback logic) and rich schema/annotations, the description is mostly complete. It lacks details on output format (no output schema provided) and does not mention rate limits or authentication needs, but covers core usage, parameters, and behavior adequately for a read-only tool.

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 baseline is 3. The description adds meaningful semantics: it explains the relationship between date parameters (specific_date vs. start/end date range), clarifies that symbols filter results (with default to all currencies), and mentions the fallback logic for unavailable dates, which the schema does not cover.

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: 'Returns historical exchange rates for a specific date or date range.' It specifies the resource (historical exchange rates) and distinguishes from siblings like 'get_latest_exchange_rates' (historical vs. latest) and 'convert_currency_specific_date' (retrieval vs. conversion).

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 historical rates, with date or date range input. It implicitly distinguishes from siblings by focusing on historical data, but does not explicitly name alternatives or state when not to use it (e.g., vs. 'get_latest_exchange_rates' for current rates).

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