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

Annotations already mark readOnlyHint=true, and the description adds meaningful behavioral context: 30-day change calculation, percentile ranking against 8.5 years of history, low/high interpretation, hourly update cadence, and the exact fields returned. This goes beyond annotations and explains the data's nature and frequency.

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 a single dense but well-organized paragraph that front-loads the core return value, then details methodology, output fields, use cases, and update frequency. Every clause adds value without redundancy, and the 'Updates: hourly' at the end is a crisp external context signal.

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 tool with one optional parameter, no output schema, and clear annotations, the description covers the return format, interpretation, use cases, update frequency, and limitation history. Together with the schema's days parameter explanation, the agent has all necessary context to select and 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 coverage is 100%, with the days parameter fully described in the schema (optional history series, Gold tier requirement). The description adds no additional parameter semantics; it mentions the current snapshot but doesn't discuss the days parameter. Baseline 3 applies because the schema carries the parameter documentation burden.

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 opens with 'Returns a 0-100 stablecoin-flow momentum score', clearly specifying the verb and resource. It defines the score's construction (30-day change, percentile-ranked) and lists output fields (trend, confidence, top_drivers, supply, 30d change %), making the tool unambiguous and distinct from siblings.

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 states when to call: 'Call when the user asks about stablecoin inflows/outflows, crypto liquidity, dry powder, or risk-on/risk-off rotation, or when timing DeFi/yield-farming exposure or crypto drawdown risk.' This provides clear contextual triggers for the agent, though it does not name a specific alternative tool.

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