explain_capability

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

Annotations already indicate readOnlyHint=true, and the description reinforces this with 'Read-only.' It adds behavioral context beyond the annotations by describing what the explanation covers: the matching rule, the tier, and other considerations. No contradiction exists, though details about edge cases such as wildcard fields or invalid inputs are absent.

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 two tight sentences: the first explains behavior and output, the second gives direct usage guidance. There is no filler or redundant restating of the tool name, and the most important information is front-loaded.

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?

The description covers the tool's purpose and relationship to mutate, and an output schema exists to handle return-value details. However, with five parameters, zero schema-level descriptions, and meaningful defaults like field='*' and direction='any', the absence of parameter guidance leaves notable gaps for correct invocation.

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 description carries the burden of explaining parameters, but it only minimally implies that 'field' is the field to change. It does not explain the required resource and operation parameters, nor the meaning of value, direction, or the '*' default. An agent would likely need external knowledge of the mutate tool's vocabulary to call this correctly.

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 a specific action ('Explain what would happen if the generic mutate tool were asked to change one field') and the expected output content ('which rule matches, at what tier, and what else was considered'). It also differentiates the tool from the sibling mutate tool by framing itself as a pre-check mechanism.

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 gives an explicit usage directive: 'Use this before mutate to find out whether a change is permitted.' This clearly identifies when to use the tool in relation to mutate, though it does not explicitly state when not to use it or mention an alternative like list_capabilities.

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