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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds valuable behavioral context beyond those: it is a paid call costing $0.001 USDC and is byte-identical to a specific GET endpoint, which clarifies side effects and cost expectations.

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 dense sentences, each earning its place: the first states output, limit, and use case; the second states cost; the third gives the exact REST equivalent. The most decision-relevant information is front-loaded, and there is no 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?

With one required string parameter, full schema coverage, existing output schema, and safety annotations, the description covers everything needed for invocation: what is returned, how many refs are allowed, the cost, and the exact endpoint semantics. No critical selection or invocation information is missing.

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. The description adds value by providing a concrete refs example (coingecko:bitcoin,base:0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) and clarifying the network:identifier format and limit, which helps the agent construct valid input beyond the schema's brief description.

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 names the exact output fields (USD price, symbol, decimals, confidence), the resource type (network:address references), and the batch limit (up to 10). It also distinguishes itself from siblings by emphasizing 'one paid call' and 'cheapest way to mark a portfolio,' making it clearly a batch snapshot tool rather than a history or single-price tool.

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 phrase 'the cheapest way to mark a portfolio' gives a clear use case and implies it is the preferred choice for batch portfolio valuation. It does not explicitly name alternatives or state when not to use it, but the context is clear enough for an agent to select it over the many market_* siblings.

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