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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), it discloses genuinely useful behavior: US-only coverage, 30-minute per-query caching, the x402/Base payment rail, that the caller's own wallet pays, and that the server never holds a wallet or pays on the agent's behalf. These are non-obvious operational traits an agent must know before invoking.

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 pricing/purpose hook is front-loaded and each sentence is substantive. There is mild redundancy — the price is stated twice and the 'server never pays on your behalf' point is made in both the intro and the payment_header description. Still reasonably tight for the amount of payment detail being conveyed.

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?

With no output schema, the description steps in to describe return values (matched coordinates for forward, containing state/county/tract/block/CBSA for reverse, plus a count/items[] alias). Combined with the fully spelled-out payment handshake, an agent has everything needed 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?

Schema description coverage is 100%, so the schema already documents q-as-alias, lat/lon pairing, address exclusivity, and the payment_header contract. The description largely restates these, though it does add the return-shape note about a count/items[] alias modeled on a comparable's field names. Baseline 3 is appropriate when the schema carries the parameter burden.

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+resource pair — forward and reverse U.S. geocoding — and names its upstream data source (Census Bureau Geocoder). It clearly enumerates the two modes via the address vs. lat/lon inputs. It does not, however, differentiate itself from the adjacent address_geocode_preview sibling, leaving the paid/preview split to be inferred from the name.

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 explicit procedural guidance: call with no payment_header first to get the challenge, then re-call with the signed header and the SAME business arguments. It also states the mutual exclusivity of the address and lat/lon input modes. It never says when to prefer this paid tool over the _preview alternative, so the when-not half is missing.

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