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

Annotations already indicate readOnlyHint=true and openWorldHint=false, and the description's 'Returns' is consistent. It adds valuable behavioral context beyond annotations, such as the data source ('USGS ASCE7 design ground motions: PGA, SS, S1') and update cadence ('Updates: on source cadence'). This helps the agent understand data freshness and provenance, going beyond the safety profile.

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 with a clear purpose: return value/scope, usage triggers, and update frequency. It is front-loaded with the most important information and avoids fluff, though it is a bit longer than strictly necessary.

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?

There is no output schema, but the description lists the key return fields (hazard_score, seismic_design_category, national_percentile, driver values, methodology_version) and the score range. This is sufficient for an agent to understand what the tool returns. It also covers the optional 'days' behavior implicitly via the schema. Minor gaps: it doesn't explain what each field means or how the historical series is structured, but these are not critical for basic selection and invocation.

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?

The input schema has one optional parameter ('days') with a complete description (100% coverage). The tool description does not add additional parameter details beyond what the schema already provides, so it meets the baseline but does not exceed it.

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 uses a specific verb ('Returns') and resource ('0-100 long-term earthquake ground-shaking hazard score for each of 3,222 US counties') with a clear scope (US counties). It also lists key fields returned, distinguishing it from generic data tools and making its purpose unmistakable.

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 states when to call the tool: 'Call when the user asks about earthquake risk, seismic hazard, ground shaking, or building-code seismic exposure for a US county or location, or when timing site-selection, property-underwriting, or retrofit-prioritization decisions.' It provides clear contextual guidance but does not mention when not to use it or suggest alternatives, so it misses the 'exclusions' part for a 5.

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