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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description contributes information the annotations do not: a cost of 1¢ per call, and the behavioral rule that the CPI frequency is inferred from the period string format. It does not cover invalid-period or invalid-item handling, but the added cost and format-coupling disclosure is meaningful.

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?

Two sentences plus a bolded price line, with the core verb and resource front-loaded and zero filler. Nothing could be removed without losing information.

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?

Parameters are fully covered by the schema and there is no output schema, so the description is not required to explain return values. However, for a pure computation tool the agent still cannot tell whether the response returns only the adjusted amount, the index ratio, or both periods' indices — a gap the description could have closed in one clause.

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%, so every parameter is already documented including the item, region and period defaults. The description adds only a light gloss ("frequency follows the period format") that overlaps the schema's own from_period wording, so baseline 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?

"Move a dollar amount between two periods using the CPI" is a specific verb+resource and immediately sets this apart from the sibling index-retrieval tools (economics_cpi, economics_cpi_latest) by framing it as a conversion rather than a data lookup. It never names those siblings explicitly, so the differentiation is inferential rather than stated.

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 two worked examples ("a 2021 median into today's dollars", "a past rent by the rents index") convey realistic when-to-use context and tie the rents example to the `item` parameter. There is no explicit when-not-to-use guidance and no pointer to economics_cpi or economics_cpi_latest for cases where the agent wants the raw index rather than an adjustment.

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