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

The readOnlyHint annotation already establishes this as a safe read operation, and the description adds useful context: the percentile ranking basis (~346 observations to 1997), output fields, and monthly update frequency. It does not contradict annotations and provides meaningful behavioral detail beyond the annotation.

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 two sentences: the first front-loads what is returned, and the second gives concrete use cases and update frequency. No filler or redundancy—each sentence earns its place.

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 is largely complete: it states output fields, use cases, update frequency, and includes the historical ranking methodology. However, it does not explain the meaning of fields like raw_std_dev, delta_12m, or regime_label, which would be useful for interpretation.

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 schema already provides 100% coverage for the only parameter (days), including its purpose and Gold tier requirement. The description does not add parameter-specific semantics, but the schema fully documents it, so a baseline of 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 the tool returns a specific 0-100 global supply-chain pressure score (GSCPI percentile) and lists the returned fields. It uses a specific verb ('returns') and names the exact resource, making it clearly distinct from the many generic sibling 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 provides explicit 'Call when...' scenarios covering supply-chain stress, shipping bottlenecks, GSCPI, logistics-driven inflation risk, and related timing decisions. It does not mention when not to use the tool or name alternatives, but the use cases are specific and actionable.

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