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

Annotations already cover safety (readOnly, idempotent, non-destructive), but the description adds substantial behavioral context: each point is the provider-reported figure at that timestamp, snapshots follow the provider's coarse ingest cadence so resolution below 1h cannot be filled, and missing buckets are absent rather than zero. These details are critical for correct interpretation and go well 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 well-structured and front-loaded with purpose, followed by data semantics and a documentation reference. It is appropriately sized for a tool with non-trivial data behavior, though the first two sentences are slightly redundant in restating the purpose.

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 moderate complexity, 100% schema coverage, rich annotations, and no output schema, the description covers purpose, data cadence, gap behavior, and resolution constraints. It stops short of describing the return structure (e.g., array of timestamp/value points) in explicit terms, but the phrase 'Each point is the figure...' gives enough to infer the response shape.

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 baseline is 3, but the description adds meaningful context beyond the schema: it explains why `resolution` must be at least `1h` (provider ingest cadence) and clarifies that absent buckets are not zero. It does not detail the exact window/resolution format, instead referring to external documentation.

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 states a specific verb and resource: 'Get reported market-cap history' and 'Returns an asset's reported market capitalisation in USD over a configurable lookback window, sampled at a configurable resolution.' This clearly distinguishes it from current-snapshot siblings like get_market_cap by emphasizing historical, lookback-windowed data.

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?

Usage is implied by the name and description—agents can infer this is for historical market cap rather than current values—but there is no explicit guidance on when to choose this tool over siblings such as get_market_cap or get_market_summary. The resolution constraint ('at least 1h') is a parameter guideline, not a when-to-use-this-vs-alternative statement.

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