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

Annotations already declare readOnly and closed-world. The description adds real value beyond that: the data source (lending contract state), default behavior (returns every currency index unless one is named), the 14 October 2026 per-stablecoin rate change, and the 'read the freshness line first' warning about data staleness.

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?

Front-loaded with what the tool returns, then the usage rationale, then the default and freshness caveat. It's dense but every sentence carries information; the long enumerations of index families make it slightly less tight.

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 read-only, single-param tool with a 100% documented enum and annotations covering the safety profile, the description covers purpose, default behavior, data source, staleness warning, and interpretation guidance. Return shape isn't described, but no output schema exists, so a complete value-level description would be a plus rather than mandatory.

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% and the enum plus its description already document the index parameter fully. The description reinforces the default (all indices) and the 14 Oct 2026 per-stablecoin distinction, but adds little syntax beyond the schema, so baseline 3 applies.

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?

States a specific verb (read) and resource (SBOR benchmark rates from lending contract state), enumerates the concrete index families (BTC-COLLATERAL-USD, per-stablecoin, Stacks currency indices), and is clearly distinguishable from siblings like get_history or compare_rate.

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?

Gives a clear use case: judge whether a lending offer is good by comparing borrow/supply rates to the benchmark, with concrete conditions (borrowing above borrow rate = overpaying). It doesn't explicitly point to sibling tools like compare_rate for cross-rate comparison, so not a 5.

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