Closes a specified browser tab by ID, including orphaned tabs belonging to your agent, to clean up session state and free resources.
Closes tab tab_id of this session (or an orphan tab of my agent).
| Name | Required | Description | Default |
|---|---|---|---|
| tab_id | Yes | Your tab's id (from browser_new_tab, or a tab adopted with browser_adopt_tab). |
Changes observed during successful MCP inspections.
v2.31.6Output schema / (root)Previous value: -{
- "properties": {
- "result": {
- "title": "Result",
- "type": "string"
- }
- },
- "required": [
- "result"
- ],
- "title": "browser_close_tabOutput",
- "type": "object"
-}New value: +nullv0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description adds the useful scope detail that orphan tabs belonging to the agent are also valid targets, but says nothing about what happens to unsaved state, closed-tab side effects, or error behavior on an unknown/stale tab_id.
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?
A single front-loaded sentence with no filler. Slight deduction because the trailing parenthetical is terse to the point of being mildly ambiguous about what 'my agent' means in practice.
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 one-required-parameter tool with full annotation coverage and no output schema, the description plus schema give an agent enough to invoke it correctly. The remaining gap is lifecycle disambiguation against sibling tab tools, which a single clause could have closed.
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% and the tab_id field description already explains provenance (from browser_new_tab or a tab adopted with browser_adopt_tab). The description adds no format, range, or validity detail beyond the schema, so the baseline 3 applies.
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 (closes) and resource (tab identified by tab_id) plus the scope of valid targets (this session's tab or an orphan tab of the agent). An agent knows what it does without opening the schema, though it does not explicitly distinguish closing from the nearby browser_release_tab / browser_adopt_tab lifecycle verbs.
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 parenthetical 'this session (or an orphan tab of my agent)' implies when the tool applies, but there is no explicit when-to-use, when-not-to-use, or pointer to the alternative lifecycle tool (browser_release_tab) for the case where the tab should be kept but disowned.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.