Get a raw ACS variable

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

The description directly contradicts the openWorldHint annotation by stating it is 'Limited to the variables held in the local store.' This is a clear closed-world claim, whereas openWorldHint implies the tool may access dynamic external data. Such a contradiction can mislead the agent about the tool's behavior.

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 compact and front-loaded with the core purpose, followed by parameter details and constraints. Every sentence adds value, and the formatting with code examples improves clarity without unnecessary verbosity.

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 two-parameter read-only lookup with an output schema present, the description covers input formats, case-insensitivity, scope limitations, and error behavior. The only flaw is the annotation contradiction, but the description itself is fully self-contained for invocation purposes.

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?

With schema description coverage at 0%, the description carries the full burden for parameter meaning and excels. It specifies zip_code as a 5-digit US ZIP and variable as either an ACS variable code or a friendly store-column name, both case-insensitive. This adds rich detail beyond the bare property titles.

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 'Raw value of a single ACS variable for a ZIP' — a specific verb+resource pair that clearly states what the tool does. The 'escape hatch' framing explicitly distinguishes it from the named sibling tools like get_income and get_demographics, which target specific variable sets.

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 'escape hatch' label provides explicit guidance: use this tool when the other, more targeted siblings don't cover a desired variable. It also notes that unknown variables error with the full list, which helps the agent understand failure mode and fallback behavior.

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