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

With annotations already declaring readOnlyHint=true, the description adds useful behavioral context: the composite construction from 5 layers, the nature of the score (0-100), the output fields, and an update cadence ('Updates: on source cadence'). It does not contradict annotations and provides more than minimal scoping, though it omits details like rate limits or data freshness specifics.

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 three sentences, each earning its place: the first defines the output and structure, the second gives invocation guidance, and the third notes update frequency. There is no redundant or filler content.

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?

The description covers the core return fields and usage scenarios, but it leaves ambiguity about granularity: does it return a score for a single county or for all counties? There is no parameter for county_fips in the schema. Without an output schema, the description should clarify this to avoid misinvocation. It also gives a vague update cadence. Overall, it is adequate but with clear gaps.

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 the baseline is 3 even though the description does not mention the optional 'days' parameter. The schema itself already fully documents that parameter, including the Gold tier requirement, so the description adds no additional parameter meaning beyond what the schema provides.

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 ('Returns') and a concrete resource: a 0-100 county movement-network strength score composed of 5 specified layers joined on county_fips. It lists exact output fields (composite_score, component_scores, drivers, coverage), making it highly distinguishable from sibling tools by topic and output.

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 says 'Call when the user asks about local transportation, transit, commute, freight, or road-network strength for a county or region, or when timing site selection, distribution-network expansion, or relocation decisions that hinge on mobility infrastructure.' This provides clear usage context, but it does not mention when not to use it or suggest alternative tools, so it stops short of a 5.

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