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

With no annotations provided, the description carries the full behavioral burden. It does disclose the core computation method (percentage decline from running peak) and implicitly clarifies this is a pure computation tool requiring the user to supply data rather than a data-fetching tool. However, it does not mention edge cases, percentage convention (e.g., 5 vs 0.05), or behavior with a single-element array.

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?

Three short sentences with zero waste: the tool name is echoed, the computation is defined precisely, and the input requirement is stated. The definition is front-loaded before the invocation instruction, and every sentence earns its place.

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 0-parameter tool with no output schema, the description covers the essential invocation requirement (supply a values array) and the computation definition. Its gaps are the unstated return format, the lack of explicit disambiguation from x402-max-drawdown, and no note on how the values are transmitted (message payload vs. context), which an agent might need to infer.

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?

The input schema is empty with 0 parameters, so the baseline is 4. The phrase 'Provide values array' adds meaning beyond the empty schema by signaling that the agent must supply the price sequence as an array, which is genuinely useful invocation guidance.

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 ('Calculate'), names the resource ('drawdown series of an asset's price'), and precisely defines the term ('percentage decline from its running peak'). It implicitly differentiates from the sibling x402-max-drawdown by specifying this computes the full series rather than a single maximum value.

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 instruction 'Provide values array' gives the agent actionable invocation context by indicating the caller must supply the price data. However, the description never explicitly states when to use this tool versus the closely related sibling x402-max-drawdown or other financial series tools, leaving the disambiguation to inference from the word 'series'.

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