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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the safety profile is clear. The description adds behavioral context about the category filter affecting result types (yields vs. prices), which is not covered by annotations. No contradictions.

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 just two sentences, both highly informative and front-loaded. Every sentence earns its place; there is no fluff.

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?

Given the tool's complexity (4 optional parameters, rich annotations, output schema exists), the description is complete. It covers primary use cases, filtering options, and critical caveats regarding category usage. No missing context for an agent to select or invoke the tool correctly.

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 description coverage is 100%, so baseline is 3. The description adds value by reiterating the category filter's importance and explaining the unfiltered call's default behavior (returns mostly spot prices). This nuance goes beyond the schema's parameter descriptions.

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 the tool's function: 'List current rates across providers, optionally filtered by symbol, category, or provider.' It also distinguishes from siblings by emphasizing the yield vs. price distinction, which is a key differentiator among similar tools.

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 explicitly provides guidance: 'For "what is the best yield on BTC right now?" style questions, ALWAYS pass category="lending"/"borrowing"/"staking" — an unfiltered call mostly returns spot prices (category="price"), not yields.' This gives clear when-to-use and when-not-to-use information.

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