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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered by structured data. The description does add genuinely useful behavior beyond that: a credit cost of 2 per call and the fact that three-month changes are gated behind paid plans, which affects whether an agent should rely on that field.

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?

A single front-loaded sentence that opens with the resource and then lists the metrics, with the plan/cost caveat trailing appropriately. The only waste is restating 'CPI Inflation' twice at the start.

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?

With an output schema present the description need not explain return values, and annotations cover side-effect behavior. What it does supply — category coverage, YoY/MoM metrics, credit cost, and paid-tier limitation — is enough for a two-optional-parameter read tool, with only sibling selection left unaddressed.

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 both the date format (YYYY-MM) and the full category list are already documented in the schema, establishing a baseline of 3. The description only reinforces that results are broken down 'by category', adding no syntax, defaults, or edge-case meaning beyond the schema.

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 names a specific resource (monthly Consumer Price Index) and enumerates the category breakdown plus the YoY/MoM metrics returned, so an agent knows exactly what data it gets. It does not distinguish itself from near-neighbours in the catalog such as InflationRate, CostofLiving, or PurchasingPower, which keeps it below a 5.

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?

There is no statement of when to choose this tool over InflationRate or other economic-data siblings, and no exclusions. The only usage-adjacent sentence ('Omit for current data', 'three-month changes on paid plans') is really parameter and plan-tier guidance, not tool-selection guidance.

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