nearest_join

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

Annotations already signal idempotence and non-destructiveness; the description adds the critical CRS safety behavior—estimated UTM measurement for geographic inputs, return in input CRS, and prevention of the classic degrees error—plus the warnings entry on emptied results. This is exactly the behavioral context an agent needs.

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 core operation is front-loaded in the first sentence, followed by two high-value caveats (CRS handling and max_distance behavior). No filler or repetition; 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 join tool with an output schema and safety annotations, this is complete: it explains the operation, the main failure mode it prevents, the distance filter, and the warning behavior. Nothing material is missing for an agent to call it successfully.

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?

With 0% schema description coverage, the description must carry parameter meaning, and it does for distance_column (IN METERS, named) and max_distance_meters (drops pairs beyond threshold). left_path, right_path, and output_path are sufficiently clear from their names, though the description does not elaborate on them.

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 operation: attach each feature's nearest neighbour from another layer and add a named distance column. The 'nearest neighbour' and 'distance in meters' wording sets it apart from the generic spatial_join sibling.

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 implies this is the tool for nearest-neighbour joins and describes conditions under which behavior changes (geographic CRS, max_distance_meters), but it never explicitly says when to use it instead of spatial_join or other siblings.

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