Style a text range

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

Beyond the annotations (readOnlyHint=false, destructiveHint=true, idempotentHint=true), the description reveals critical behaviors: partial-update masking, explicit false turning toggles off, empty link_url removing existing links, and index stability across calls. These details materially help an agent predict side effects and reuse the tool safely.

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 compact and front-loaded: the first sentence states the operation and enumerates formatting options; the following sentences each add a distinct behavioral constraint. No sentence is filler, and the density is justified by the tool's 16-parameter surface.

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 complex, high-parameter mutation tool with no output schema, the description is remarkably complete: it covers all formatting fields, partial-update semantics, toggle behavior, link removal, index sourcing, and index stability. The only omission, the exact return value, is not essential for a write-oriented tool and is not promised by the annotations.

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 100%, so the schema already documents every parameter's format and meaning. The description adds valuable semantic context on top: the fields-mask behavior, the meaning of explicit false for boolean toggles, and the empty-string behavior for link_url. This goes beyond the baseline but is not exhaustive for all 16 parameters.

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 specific action ('Applies character formatting') on an explicit resource (a text range given by start/end indexes) and enumerates the exact formatting dimensions it affects. This clearly distinguishes it from sibling tools like style_paragraph, which targets paragraph-level formatting.

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 concrete usage guidance: obtain indexes from read_document_text, and multiple style calls can reuse the same coordinates because styling does not shift indexes. It also explains the partial-update semantics ('Only the provided fields change') and the requirement that at least one field be provided. It does not explicitly contrast this tool with style_paragraph or other siblings, but the character-range scope makes the intended use clear.

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