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

The description adds important behavioral caveats beyond the readOnlyHint and idempotentHint annotations: estimates are interpolated, roughly hourly, exclude fees, and are not executable quotes. This helps the agent avoid misusing the results.

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 sentences with no filler: the core function is front-loaded, followed by caveats, then a pointer to the alternative tool. 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 single-parameter, read-only tool with no output schema, the description is complete: it explains the output type, the estimation limitations, and how to get comparison/freshness information from a sibling.

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 schema already documents size_usd and the nearest-rung behavior with 100% coverage. The description repeats the 'nearest published USD rung' concept but adds no new parameter-level meaning, so the baseline 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 names a specific resource and operation: 'BTC sell-cost estimates by venue at the nearest published USD rung.' It clearly distinguishes itself from the sibling crypto_exit_check by positioning that tool as the comparison/freshness alternative.

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 final sentence explicitly routes the agent to crypto_exit_check when comparing sizes and freshness, giving a clear alternative and trigger condition. It implies this tool is for single-size, current-rung sell-cost estimates.

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