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

Goes well beyond the readOnly/openWorld/idempotent annotations: discloses the Photon source with Nominatim fallback, that empty ocean or unknown coordinates yield a 404 and are not charged, and the full payment behavior ($0.001 USDC on Base via x402, with an unauthenticated call returning a PaymentRequired object). This is exactly the kind of cost and failure-mode context annotations cannot carry.

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?

Front-loads the trigger condition, then the return shape, then failure and payment semantics — a sensible priority order. It is dense but every clause carries operational information; only the pricing sentence is slightly heavy for a selection-time read.

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 must describe the response, and it does: display name, country, city, street when available, plus the matched feature's coordinates. Combined with the 404 behavior and payment flow, an agent has everything needed to call and interpret results.

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% and both lat/lon bounds are documented in the schema, so the baseline is 3. The description only alludes to the coordinates and the matched feature's lat/lon without adding format or precision guidance.

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?

States a specific verb+resource pair: coordinates in, human-readable place out, and enumerates the returned fields (display name, country, city, street, matched lat/lon). The coordinate-input framing cleanly distinguishes it from the name-based siblings geocode and geocode_search.

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?

Explicitly says when to use it (agent has coordinates from GPS, a map click, or another API) and what condition triggers it. It does not name the forward-geocoding alternative the way the calibration's top example does, so routing is implied rather than stated.

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