show_fx_history

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

Without annotations, the description discloses that the tool reads a local cache (non-destructive), details the two output modes, and notes USD is always 1.0. No mention of auth or rate limits, but the read-only nature is clear.

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 three efficient sentences, each earning its place. The first sentence states purpose, the second explains the two modes, the third notes the USD exception. No words wasted.

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 no output schema, the description explains return types: for no currency, count + first/last date; for currency, cached series with date range or limit. It covers the USD edge case. Lacks exact format of series rows, but sufficient for a cache inspection 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 coverage is 100%, baseline 3. The description adds context: without currency produces summary, with currency yields series, limit applies only when no date range, and USD behavior. This meaningfully extends the schema descriptions.

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 inspects the local FX rate cache and distinguishes two modes: without currency returns per-currency coverage summary (count + first/last date), with currency returns cached series. It also specifies USD has no rows, which adds precision.

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 usage for two modes: omit currency for coverage summary, include currency with optional date range or limit for series. It does not compare to sibling tools but internally guides parameter choice well.

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