fill_input

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

With no annotations, the description carries the full burden and meets it. It discloses side effects (modifies DOM value, triggers input/change events), prerequisites (element exists, visible, input/textarea/contenteditable), and return type (success confirmation). This is thorough behavioral disclosure.

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 well structured and efficient: opening action, side effects, prerequisites, return, usage, alternatives. Every sentence provides distinct value with no redundancy or fluff.

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 4-parameter tool with no output schema, the description fully covers what the tool does, when to use it, behavioral side effects, prerequisites, and return value. It is complete enough for an agent to select and invoke it correctly without ambiguity.

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 100% and each parameter has a detailed description already. The tool description adds only general context ('CSS selector', 'input/textarea/contenteditable') already present in the schema. Baseline 3 is appropriate since the schema handles parameter semantics.

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?

States a specific verb ('focuses', 'inserts text') and resource ('input field via CSS selector'), and explains the native input simulation with event triggering. It distinguishes itself from siblings by naming evaluate_js and click_element as alternatives.

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 states when to use: 'Use this to populate form fields, search boxes, text areas.' It also gives clear alternatives and their distinguishing conditions: evaluate_js for direct value 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.