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

Adds substantial context beyond the readOnly/openWorld annotations: free-tier quota (3 calls/day across all tools), price and payment mechanism ($0.0015 USDC via x402 or card, paid in-band through params._meta['x402/payment']), caching, and ODbL attribution requirements. These are behavioral facts an agent cannot get from structured fields.

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?

Dense but front-loaded and largely waste-free: pricing/quota, then capability, then usage. The pricing clause arriving first slightly buries the actual capability, but every sentence carries information.

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 an output schema present, return values needn't be explained, and the description still names the key returned fields (structured address, country code, bbox, OSM id). Minor gaps: no guidance on error/no-match behavior or whether q and lat/lon are mutually exclusive.

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 baseline is 3. The description reinforces a few semantics — country as an optional filter, limit as 'up to 5 matches', and lat+lon pairing for reverse mode — but adds little that the schema does not already state.

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 and resource ('Geocoding with OpenStreetMap Nominatim') and covers both directions: address/place -> coordinates and lat+lon -> structured address. An agent can tell what it does, though it never mentions the sibling geocode_batch, so the batch-vs-single distinction is left implicit.

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 'When to use' line restates the purpose rather than giving real selection criteria — it names no alternatives (e.g., geocode_batch for multiple addresses) and no exclusions. Usage is implied by the forward/reverse mode split but not genuinely guided.

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