Forex OHLC bars

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows it's a read operation. The description adds behavioral context: volume is always 0 for OTC spot forex, and that large ranges may be truncated with a note. This goes beyond annotations without contradiction.

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 two sentences long, front-loaded with the main action and key constraints. Every sentence provides essential information without redundancy or fluff.

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?

No output schema exists, so the description must cover what is returned. It mentions OHLC bars and the _truncated note for large ranges. It also explains volume behavior. With 6 parameters and 2 required, the description covers core aspects adequately, though it doesn't detail the exact bar structure (e.g., fields returned). Still, it is sufficient for an experienced agent.

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%, so the schema defines all parameters. The description adds meaning: explains the default interval ('default 1m'), specifies pair format ('6-character FX pair'), and clarifies pagination mechanism ('paginate with cursor/limit'). This adds value over bare schema.

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 it fetches historical OHLC bars for a 6-character FX pair, specifying pair format, time range, and interval. It distinguishes from sibling tool last_quote by stating 'For the current rate use last_quote.' This provides a specific verb+resource with scope.

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 explicitly tells when to use this tool (historical bars) and when not ('for the current rate use last_quote'). It provides guidance on handling large ranges: 'Large ranges are size-capped (watch for the _truncated note) — narrow the range or paginate with cursor/limit.' This is clear and actionable.

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