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

With no annotations provided, the description fully discloses behavioral traits: side effects (modifies DOM, triggers events), prerequisites (element existence/visibility/type), return value (success confirmation), and interaction details (replaces existing text, triggers events). No contradictions exist.

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?

Front-loaded with core functionality, each sentence adds value: first explains the action, second covers side effects, third lists prerequisites, fourth states returns, fifth gives usage examples, and sixth provides alternatives. Zero wasted words.

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 2-parameter tool with no annotations and no output schema, the description is complete: it covers purpose, behavior, prerequisites, returns, usage context, and alternatives. No gaps remain given the tool's complexity and available structured data.

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 baseline is 3. The description adds meaningful context beyond the schema by explaining the overall interaction ('replaces any existing text after focus') and tying parameters to the tool's purpose, though it doesn't provide additional syntax details for the parameters themselves.

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 specific action ('focuses an input field... and inserts text') and target resource ('input field via CSS selector'), distinguishing it from siblings like 'evaluate_js' or 'click_element' by specifying native input simulation with event triggering.

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?

Explicitly provides when to use ('populate form fields, search boxes, text areas'), when not to use (prerequisites like element must exist/be visible), and names specific alternatives ('evaluate_js' for direct assignment without events, 'click_element' to focus manually).

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