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

Beyond the annotations (readOnlyHint=true), the description adds meaningful behavioral context: the scoring methodology, data source (DeFiLlama), update frequency (hourly), and a Gold-tier requirement for historical data. It also clarifies the default behavior when the optional parameter is omitted (snapshot returned). No contradiction with annotations exists.

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 zero filler. The first sentence packs the core purpose, methodology, and output fields; the second gives use cases; the third states the refresh rate. All information is relevant and front-loaded, making it easy for an agent to quickly parse.

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 has no output schema, the description compensates by listing the output fields and the nature of the return (snapshot vs. history). It also covers update frequency and access tier. Minor gaps: does not describe the exact response format/structure or error conditions, but these are not critical for selecting and invoking the tool.

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 fully describes the single optional parameter `days`, including its range (1-1825) and behavior (returns history series instead of snapshot; Gold tier required). The description itself does not add parameter-level detail beyond what the schema already provides, so the baseline of 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?

The description leads with a specific verb+resource: "Returns a 0-100 USD-stablecoin market health score" and precisely defines the score composition (50% 30-day total-mcap growth + 50% peg health). It also lists the concrete output fields (total_mcap, top-8 stablecoin prices, off_peg_count, 30-day history), making the tool's function unmistakable.

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?

Explicitly states when to call: "Call when the user asks about stablecoin market growth, USDT/USDC peg stability, or depeg risk, or when timing stablecoin float sizing, collateral rotation, or settlement-rail decisions." This covers several concrete use cases. However, it does not mention when NOT to use it or point to alternative sibling tools, so it misses the 'when-not/alternatives' part of the 5-level criterion.

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