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

Annotations already declare readOnlyHint=true, and the description aligns with that by noting it reads from lending contract state. It adds useful behavior beyond annotations: returns every currency index unless one is named, and the freshness line instruction. These are behavioral details not present in annotations, so it earns a solid 4.

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 three sentences with no wasted words. It front-loads the purpose, then adds usage guidance and a critical operational hint. Every sentence earns its place, and the structure is clear and scannable.

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 read-only tool with one optional parameter and no output schema, the description covers purpose, usage, return behavior (all indices unless specified), and a freshness warning. It does not specify the exact response format or potential error cases, but given the low complexity and existing annotations, it is adequately complete.

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 has 100% coverage with a detailed enum description for the optional index parameter, including the meaning of BTC-COLLATERAL-USDC and the omission behavior. The description adds nothing beyond what the schema already provides, so a baseline 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 clearly states it fetches the benchmark borrow and supply rates for lending on Stacks, with a specific verb ('get') and resource ('rate'). It also explains the practical use case (judging whether an offer is good), which adds clarity. However, it does not explicitly differentiate from sibling tools like compare_rate or compare_chains, so it loses a point.

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 provides concrete usage context: borrowing above the SBOR rate is expensive, supplying below the supply rate is cheap, and it instructs to read the freshness line first. This tells an agent when and how to use it, but it does not explicitly state when not to use it or mention alternative tools, which keeps it from a 5.

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