frankfurter_historical

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

Beyond annotations (readOnlyHint, destructiveHint, openWorldHint), the description adds key behavioral insights: data availability from 1999-01-04, weekend/holiday fallback logic, and that rates are not real-time. 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?

Three concise sentences, front-loaded with the core purpose, no unnecessary words. Every sentence adds value: what it does, what it is not, data availability, and edge-case handling.

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 simplicity, no output schema, and adequate annotations, the description fully covers the necessary context: purpose, data source (ECB), historical scope, non-real-time nature, and behavior on non-business days. No gaps.

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 documentation coverage is 100%, so parameters are well-documented in the schema itself. The description mentions date and implicitly base currency (default USD in schema), but does not add significant new semantic value beyond what the schema already provides for any parameter.

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 retrieves ECB forex exchange rates for a specific past date, distinguishing it from sibling tools like frankfurter_latest (current rates) or frankfurter_timeseries (date range). Verb 'Get' plus resource 'exchange rates for a specific past date' is precise.

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?

Explicitly notes these are daily reference rates not real-time trading rates, and explains behavior on weekends/holidays (returns previous business day). While it doesn't explicitly name alternative tools for real-time or latest rates, the context with sibling tools provides clear alternatives.

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