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

Annotations already declare readOnlyHint=true, and the description adds refresh cadence ('Updates: on source cadence') and the list of returned fields (score, top_drivers, confidence, etc.). It does not explain how county selection works, which is a minor gap, but the overall behavior is well disclosed.

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 two sentences plus a short update note. It is front-loaded with the primary function, concise, and contains no redundant filler. Every sentence contributes useful 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?

Despite the description specifying 'for any of 3,222 US counties', the input schema has no county parameter, leaving it unclear how an agent selects a specific county. The tool appears to return a snapshot for all counties, but this is not stated. The description lists output fields but lacks essential usage context around county selection, and there is no output schema to clarify the response shape.

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 description coverage is 100% for the only parameter 'days', which is fully documented with its optional daily history behavior and Gold tier requirement. The main description adds no extra parameter semantics beyond what the schema already provides, so the baseline score of 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?

The description clearly states the tool returns a 0-100 historic-heritage richness score for 3,222 US counties, with a specific list of output fields. This distinguishes it from sibling tools like air quality or cancer risk indices, and the mention of 'old-town character' adds specificity.

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 explicitly lists when to call the tool: when users ask about historic sites, heritage tourism, or old-town character, and when doing itinerary routing, hotel selection, or heritage-market screening. However, it does not provide exclusions or mention alternative tools for non-heritage queries.

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