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

Annotations already indicate read-only, idempotent, open-world behavior. The description adds valuable behavioral context: it returns nearby BFE lines and distinguishes 'outside floodplain' from 'never mapped', which is not derivable from annotations. No contradiction found.

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 concise (two sentences) and front-loaded with the core purpose ('AUTHORITATIVE flood-zone lookup'). It packs significant detail without unnecessary fluff, and the usage preference is clearly stated.

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 read-only, idempotent tool with no output schema, the description adequately enumerates the returned fields (zone code, subtype, SFHA flag, BFE, DFIRM id, nearby BFE lines) and explains a critical distinction ('outside floodplain' vs 'never mapped'). This is sufficient for an agent to call it correctly.

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 schema already provides 100% coverage with descriptions for all parameters. The description mentions 'nearby base flood elevation lines' which aligns with include_bfe, but adds little beyond the schema's own documentation. It does not add new meaning to latitude/longitude beyond what is already stated.

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 function: given a latitude/longitude, return the FEMA FIRM flood zone with specific outputs. It uses a specific verb ('lookup') and resource ('flood zone'). It distinguishes itself from web search but does not explicitly mention sibling tools like nfhl_layers or nfhl_query, so it falls short of a 5.

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 to prefer this tool over web search for flood-zone and insurance queries, providing clear usage context. However, it does not mention when not to use it relative to the sibling nfhl tools, so it lacks a full exclusion set.

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