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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds value by detailing the output shape (per-month entries with specific fields) and the parameter format (YYYY-MM or YYYY), going beyond the annotations. No contradictions.

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 with zero waste. The first sentence states purpose and required parameter; the second details output and optional filters. Front-loaded and efficient.

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's simplicity (4 parameters, rich annotations, no output schema), the description covers purpose, parameter format, output fields, and source reference. It could be improved by explicitly stating the return type (array of entries) or handling of the lang parameter, but overall is adequate.

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 baseline is 3. The description adds meaningful context beyond schema: it explains the date format for start_period/end_period, clarifies the example code (120010 = CPI General), and describes the computed fields (percent, percentYear) that the parameters don't directly cover.

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 it fetches monthly values for a CBS price index, specifying the required numeric code from index_catalog and the returned fields (index value, percent change, year-over-year change). It distinguishes itself by referencing index_catalog as a prerequisite and mentioning 'Israeli inflation', which differentiates it from generic index 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 usage context (fetching from CBS, using code from index_catalog, optional period filtering) but does not explicitly compare with siblings like get_series_data or state when to avoid this tool. The guidance is implied but lacks direct alternatives or exclusions.

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