Get historical market chart

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

Annotations already mark the tool as read-only and non-destructive. The description adds valuable behavioral details: long windows are down-sampled to max_points evenly spaced observations, and change_percent is always computed from the full series. This goes beyond the annotation safety profile, explaining the data processing 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 two well-structured sentences that are front-loaded with the primary purpose and immediately add important caveats about down-sampling. No redundant information or filler.

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 moderate complexity (5 parameters) and the presence of an output schema, the description is complete enough. It covers the core behavior, down-sampling, and the change_percent calculation. It does not explicitly mention the paid-plan limitation for some intervals, but that is already in the schema parameter description, so no major gap exists.

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 baseline is 3. The description adds meaning by clarifying the interplay between 'days' and 'max_points' via the down-sampling note, and explains that change_percent is computed from the full series, which affects understanding of the output. This is extra value beyond the schema definitions.

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 uses a specific verb ('Get') and names the exact resource: 'historical price, market cap, and volume series for a coin over a look-back window.' This clearly distinguishes the tool from siblings like get_historical_price or get_ohlc_candles by emphasizing the multi-series market chart output.

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 intended use case: obtaining historical market chart data for a coin. It does not explicitly mention alternatives or exclusions, but the phrase 'market chart' and the mention of down-sampling provide clear context for when this tool is appropriate.

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