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

Annotations already cover the safety profile (readOnly=true, idempotent=true, destructive=false). The description adds genuinely new behavioral context: the request is 'bounded' and capacity shifts by mode (5 in demo, 10 in production), which annotations cannot express. No contradiction with annotations.

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, zero filler. The core action and scope are front-loaded in the first sentence, and the second sentence adds the operational limit. Every word 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?

For a single-parameter, read-only lookup with fully documented schema and safety annotations, the description is nearly complete. The only notable gap is that it never defines what a 'ZIP profile' contains, and there is no output schema or sibling reference to fill that in, though the sample schema for zip_codes implies the input context.

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 value beyond the schema by revealing the mode-dependent cap (demo 5 vs. production 10), which supplements the schema's static maxItems=10 and clarifies the practical bound an agent should respect.

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 states a specific verb ('look up') and resource ('ZIP profiles') and clarifies the batch nature with 'multiple' and 'one bounded request.' It is clear but does not explicitly name the sibling it differs from (geo_zip_lookup), so differentiation is implied 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 demo/production capacity distinction gives useful context for when the tool is appropriate, and 'multiple' implies batch use. However, it never explicitly states when to choose this over geo_zip_lookup or names any alternative, leaving usage guidance to inference.

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