Bulk ZIP Code Lookup

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true. The description adds value by specifying the return format (array with city, region, country, codes, coordinates) and the batch limit of 100. It does not cover error handling or rate limits, but for a read-only tool the disclosure is adequate.

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 concise sentences: the first states the core action, the second adds the optional filter. No extraneous words. Every 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?

Given the tool's simplicity (2 parameters, no output schema, annotations present), the description covers the input constraints (max 100 codes, optional country) and output structure (array with city, region, coordinates). It is mostly complete, though missing error behavior or specific response examples.

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% with good parameter descriptions. The description reinforces the batch limit (up to 100) and the optional country filter, but does not add significant new meaning beyond what the schema already provides. Baseline 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's purpose: 'Look up details for up to 100 ZIP/postal codes at once.' It specifies the resource (ZIP/postal codes), the action (look up), and the scope (up to 100 in bulk). This distinguishes it clearly from siblings like 'zipcode_lookup' (single lookup) and other zipcode 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 implies usage for multiple codes ('up to 100') and optionally filtering by country, but does not explicitly state when to use this tool versus alternatives (e.g., 'use zipcode_lookup for a single code'). No exclusions or alternative names are provided.

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