fxa_candles

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds valuable details beyond the schema: higher timeframes are aggregated from M1 on true clock boundaries, and it returns the most recent bars when the range exceeds the limit. This gives the agent realistic expectations about data generation and edge-case behavior.

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 sentences with no wasted words. It front-loads the core purpose in the first sentence, then adds two concise, high-value behavioral notes. Every sentence earns its place and the structure is easy to scan.

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 moderate complexity, the description covers the primary input space (instrument, date range, timeframe), key behavioral rules (aggregation and limit overflow), and the expected output concept (OHLC candles). The absence of an output schema is partially mitigated by the 'OHLC candles' context. It could perhaps mention ordering or timezone, but it is reasonably complete for a fetch 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 schema already documents all five parameters. The description adds some high-level context (e.g., 'over a date range', 'any timeframe from M1 to W1') but does not introduce new parameter-level details that are absent from the schema. It effectively reinforces, rather than expands on, the 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 the tool fetches OHLC candles for an instrument over a date range, with explicit timeframe support from M1 to W1. It uses a specific verb ('Fetch') and resource ('OHLC candles') that distinguishes it from sibling tools like fxa_level_touches or fxa_bucket_stats.

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 implies the primary use case (fetching candle data for an instrument over a time range) but does not explicitly state when to prefer this tool over alternatives or mention any exclusions. It provides useful context about aggregation and limit behavior but lacks direct comparative guidance.

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