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

Beyond the annotations (readOnly, idempotent, non-destructive, closed-world), the description adds real behavioral context: the geographic restriction, the derivation method ('Census ZIP-area center point'), an accuracy caveat, and the fact that a member's position record is only included if public. It stops short of describing the response shape, but that is not critical here.

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?

One dense sentence plus a short caveat sentence, with the limiting scope 'North Carolina only' front-loaded. Slightly run-on, but every clause carries information and nothing is wasted.

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 lookup with no output schema, the description covers who it applies to (NC), how the match is made (ZIP center point), what comes back (House/Senate districts, office pages, public position records), and the main accuracy risk. An agent has everything needed to call it and interpret the answer appropriately.

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 single 'zip' parameter (pattern ^\d{5}$, described as '5-digit ZIP code'). The description restates 'from a 5-digit ZIP' without adding format or edge-case detail, so the schema is doing the work; 3 is the appropriate baseline.

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 and resource ('from a 5-digit ZIP, find the NC House and Senate districts... and the public office pages of those members') and immediately scopes it ('North Carolina only'). None of the sibling tools (bill_status, nc_legislation, latest_news, etc.) do geographic legislator lookup, so the agent can route to it unambiguously.

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?

It gives clear triggering context ('from a 5-digit ZIP') and a caution about when the result may be off ('ZIPs can cross districts, so confirm with the official lookup'). It does not name a sibling alternative or state explicit exclusions, but no sibling genuinely overlaps for this task.

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