Field Calculator

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

No annotations exist, so the description carries the burden. It notes in-place modification and returns feature count, but the phrase 'Add (if missing)' is ambiguous about behavior when field already exists. Lacks disclosure on permissions, error handling, or reversibility.

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 concise (one sentence plus example) and front-loads the core action. However, it could be more structured with bullet points or clearer separation of parameter details.

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 6 parameters, no output schema, and no annotations, the description is incomplete. It does not cover edge cases, error states, or full parameter semantics, leaving significant gaps for an AI agent to use correctly.

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 coverage, the description must compensate. It explains field_type with defaults and gives an example using expression and field_name, but does not explain layer_id, length, or precision. Missing parameter details limit usability.

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 states it adds and populates a field from a QGIS expression per feature in-place, with an example. It is specific and differentiates from generic sibling tools like add_field or evaluate_expression, though not explicitly.

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 usage for adding a computed field but does not explicitly state when to use this tool over alternatives like add_field or evaluate_expression. No direct comparison or exclusion criteria.

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