Find River Mile Markers Near a Location

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

The annotations already state readOnlyHint=true, destructiveHint=false, and idempotentHint=true. The description adds value beyond annotations by explaining that results for point queries include 'distance_m' and are sorted nearest-first, that geometry queries return intersecting markers, and that the 'truncated' field indicates more matches exist. It also lists error responses. This is above and beyond what annotations provide, though the output schema (which exists) already documents the return format, slightly reducing the need for that detail.

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 description is well-structured with clear sections (purpose, usage patterns, return format, error responses). It is fairly concise for the amount of information provided, but could be slightly trimmed (e.g., the full error list could be summarized as 'See error responses: ...'). Still, nearly every sentence earns its place.

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 tool with 5 parameters, 100% schema coverage, a detailed output schema, and comprehensive annotations, the description is nearly complete. It explains the two usage modes, result sorting, truncation behavior, and error cases. The only minor gap is that it does not explicitly state what happens when no markers are found (though the output schema structure implicitly shows count=0). Overall, very well-rounded.

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%, providing solid baseline. The description adds limited extra semantics beyond the schema—it explains the dual-mode logic and gives usage examples, but the schema already covers descriptions for each parameter decently. The description does not add new constraints or format details for parameters that aren't already in the schema. Baseline 3 is appropriate.

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 clearly specifies 'Find USACE river mile markers near a point or within a geometry', using a specific verb ('Find'), a distinct resource ('USACE river mile markers'), and the operation's dual modes (point+radius or geometry). It explicitly distinguishes itself from siblings by not being the 'nearest' or a generic 'query' tool.

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 description provides explicit when-to-use guidance with concrete query examples for both lat/lon and geometry modes, and clearly warns 'supply either lat+lon or geometry, not both (or neither)'. This fully addresses when and how to choose between usage patterns, earning a top score.

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