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

The description adds substantial behavioral context beyond the annotations: the 0.05 USDC per-call cost, the start dates for quote and spot series, and the fact that each row carries its data source. These details are not present in the annotations and meaningfully inform the agent about side effects and data provenance.

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 compact and front-loaded: it opens with the paid cost, then the core purpose, then the relevant data availability notes. Every sentence carries useful information without redundancy.

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 relatively simple read-only history tool, the description covers the main invocation concerns: what it returns conceptually, the date-range scope, pricing, and data source availability. It does not detail output columns or pagination, but with no output schema and low parameter complexity, the description is sufficiently complete for an agent to select and call the 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 baseline is 3. The description reinforces the date-range concept and provides availability context, but it does not add new semantics for the ticker, from, or to parameters beyond what the schema already states.

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 resource and action: 'Daily fixings for a ticker over a date range.' It is not a tautology and gives enough specificity to understand the tool's purpose, but it does not explicitly name sibling tools to differentiate itself, so it stops short of a 5.

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 gives clear context: this tool provides daily fixings over a date range, with pricing and data availability details. It implies when to use it, but it does not explicitly state exclusions or name alternatives such as index_fixing or spot_daily, so it lacks full when-not guidance.

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