Set a form field's value directly in a Firefox tab using a CSS selector, avoiding simulated typing. Target the active or a specific tab by ID.
Set a form field's value directly (faster than typing).
Args: selector: CSS selector of the input/select element value: Value to set tab_id: Optional tab to target. Defaults to active tab.
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | ||
| tab_id | No | ||
| selector | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full behavioral burden. It notes the direct-set approach and the active-tab default, but omits the critical trait of direct value assignment: whether input/change events fire, whether it works on select/checkbox elements, and whether prior values are overwritten. For a mutation tool with zero annotation coverage this is a significant gap.
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 purpose is front-loaded in one sentence and the args list is compact, with the speed differentiator given prominence. The args list largely duplicates the schema property names but is justified given 0% schema coverage.
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?
A mutation tool with no annotations and no output schema should disclose event semantics, failure behavior (e.g., selector not found), and result shape. None of that is present; the definition is adequate only for a rough 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 is the only source of parameter meaning. It does document all three parameters and adds slightly useful detail ("CSS selector of the input/select element", tab_id optional with active-tab default), but "value: Value to set" is pure restatement and no formats or examples are given.
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 and resource ("Set a form field's value") and adds a differentiating clause ("faster than typing") that separates it from the sibling browser_type. It does not, however, distinguish itself from browser_form_fill or browser_set_editable_content, which also mutate field content.
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?
"Faster than typing" implies the selection rule against browser_type, so usage is inferable. There is no explicit when-to-use vs when-not-to-use, no mention of browser_form_fill (multi-field filling) or browser_select_option (dropdowns), so the agent must guess which form mutation tool applies.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.