Evaluate Expression

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

Annotations already declare readOnlyHint=true, indicating it is a read operation. The description reinforces this by stating 'evaluate to a scalar value' and gives expression examples, but does not add significant behavioral context beyond what annotations provide. No contradictions.

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 extremely concise: two sentences that front-load the purpose and include examples and sibling differentiation. Every sentence adds value with no redundancy.

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?

No output schema exists, but the description describes the result as a 'scalar value', which sets expectations. It covers the tool's main functionality and differentiates from key siblings. It could be more complete by noting that the returned value's type depends on the expression, but overall it is adequate for a straightforward tool.

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 0% (no descriptions in input schema). The description mentions 'expression' and 'layer_id', noting that layer_id is optional and adds scope, and gives example expressions. However, it does not specify expression syntax constraints, accepted formats, or potential errors, leaving gaps for an agent.

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 the tool 'evaluates a standalone QGIS expression to a scalar value', provides concrete examples (aggregate, @project_var, now()), and explicitly distinguishes it from two siblings (validate_expression and field_calculator). This provides high specificity and differentiation.

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 mentions 'Optional layer_id adds layer scope' and distinguishes from siblings, giving implicit guidance on when to use this tool vs. alternatives. However, it does not explicitly state when not to use it or provide clear prerequisites, which would improve score.

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