Deribit Mark Price History

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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds crucial expected behavior: mark price history is only retained for options involved in volatility index calculation, and empty results for futures/perpetuals are normal. This disclosure prevents misinterpretation of empty arrays as errors, which is highly valuable beyond the 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?

The description is two sentences: the first states the action and return format, the second provides a critical caveat. No redundant information, and the important behavioral note is included without extra verbosity.

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 simple 3-parameter read-only history tool, the description covers what it returns, the units, and the unusual empty-result case. Annotations cover safety, and the schema covers parameters fully, so nothing critical is missing for an agent to use the tool correctly.

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% with all parameters documented (instrument_name with examples, timestamps with units). The description only confirms the millisecond unit for timestamps, which is already present in the schema. Thus, the description adds little beyond the structured schema, so a baseline score of 3 is appropriate.

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 ('query') and specifies the resource ('historical mark price series for a contract') plus the exact return format ([timestamp, mark price] pairs). The note about futures/perpetuals returning empty arrays distinguishes it from similar market data tools.

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 clearly notes that futures and perpetuals will return empty arrays, which implies this tool is intended for options that participate in volatility index calculation. While it doesn't explicitly name alternative tools when futures/perpetuals are queried, the behavior warning provides enough context for an agent to decide 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.