Official exchange rates

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

Annotations already mark it read-only, idempotent, non-destructive, and open-world, but the description adds important behavior: official vs free-market rate scope, empty-list behavior for missing dates, and interpretation of per_units and trend. These are meaningful details beyond the structured 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?

Front-loads the tool's purpose, then efficiently covers official-rate caveat, return-field semantics, empty-result behavior, and the sibling alternative. Every sentence is useful and nothing is redundant.

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?

For a two-parameter read-only tool with no output schema, the description supplies enough context to call and interpret it: date coverage, currency coverage, official-rate meaning, empty-result behavior, and the key return concepts. No critical gap remains for agent selection or invocation.

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 both input parameters are already well documented in the schema. The description adds useful context about official-rate scope and return fields like per_units and trend, but it does not add much input-parameter semantics beyond what the schema already provides.

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?

States a specific verb and resource: retrieves the Central Bank of Iran's official reference exchange rates for one day, in rials per currency unit. It also distinguishes official rates from free-market rates and names cb_rate_history for multi-day series, so an agent can distinguish it from siblings.

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 says to use it for today or any past day back to 1383/2004, clarifies these are official not free-market rates, and directs series requests to cb_rate_history. It also explains that weekends, holidays, and future dates return an empty rates list.

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