get_unique_values

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

With no annotations, the description carries the full behavioral burden. It discloses the limit behavior ('Max number of unique values to return') and the exact-layer-name requirement, but it does not mention ordering, null handling, or what happens when the field contains more unique values than the limit. This is sufficient but incomplete.

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 short and front-loaded with the core action, followed by a practical use case and a compact argument list. Every line earns its place without unnecessary prose or repetition.

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?

This is a simple read-only tool with an output schema and all parameters documented, so the description is largely complete for an agent to invoke it. The main gaps are edge-case behaviors such as ordering and truncation when unique values exceed the limit, which would improve completeness.

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 0%, so the Args block is the only parameter documentation. It meaningfully explains all three parameters: layer must match the Contents pane exactly, field identifies the target field, and limit explains the default and maximum return size. This fully compensates for the schema's lack of descriptions.

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 states a clear action and resource: 'Get all unique values in a field.' This distinguishes it from sibling tools like list_fields (field names) and get_layer_features (feature records), and the mention of building WHERE clauses for select_by_attribute gives immediate practical context.

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 phrase 'Useful for exploring data and building WHERE clauses for select_by_attribute' gives a clear when-to-use context and connects it to a specific sibling workflow. It does not explicitly state when not to use it or name alternative tools, so it stops short of a 5.

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