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

Annotations already cover safety (readOnly, idempotent, non-destructive), but the description adds real behavioral context: the result shape '{ data: StationPrice[] }', that stations without a price are dropped from results, default and maximum values for radius and limit, and the auth requirement of partner keys with partner_tenant_ref on every call. This is information an agent cannot get from the annotations or schema.

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?

Four dense sentences, front-loaded with the identity and data source, then return shape, then defaults/limits, then the auth constraint. Nothing is padded and the most actionable constraint (partner keys) sits at the end where it is easy to catch.

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 correctly supplies the return wrapper and the key filtering behavior (unpriced stations omitted), plus limits and auth. It does not describe what fields a StationPrice contains, which is the remaining gap for a consumer of the response.

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%, so baseline is 3; the description goes beyond it by supplying the defaults the schema omits (radius default 10, limit default 50) and the units of radius (miles). The partner_tenant_ref requirement is also reinforced, though include_estimated is not touched on.

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 (posted retail diesel prices at truck stops), the geographic scope (near a point), the ordering (nearest first), and the data source. An agent can immediately distinguish this from diesel_price_station (single station), fuel_market_snapshot (market-level), and optimize_fuel_plan (planning).

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?

Usage is implied by 'near a point' plus the radius defaults, and the partner-key prerequisite ('send partner_tenant_ref with every call') is a genuine usage constraint. However, it never states when to prefer this over a sibling like diesel_price_station, nor any exclusion such as coverage limits.

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