BCD — Bridge Control Delegate

app_increment

Step a slider, stepper or other adjustable element of the latest app_snapshot up by one step. Returns the app's new state with the next snapshotId, so no extra snapshot is needed. If the window changed, or a person used the keyboard or mouse in the app since the snapshot, nothing is done and the error comes with the current state to retry from. A sent action is not proof the task succeeded. Needs ui and process permission (operating apps can run programs).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "snapshotId": "<snapshotId>",
      "elementId": "<elementId>"
    },
    "name": "app_increment"
  }
}

Input Schema

Name	Required	Description
`deviceId`	No	Computer name or id from list_devices. Optional with one computer online or a default set.
`takeOver`	No	Only when the user says so: act even though another conversation is operating this screen, which then holds it no longer.
`elementId`	Yes
`snapshotId`	Yes
`workSessionId`	No	Work session from create_work_session. Pass the same ID on every call in this conversation; omit for legacy unscoped work.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 23, 2026

addedInput schema / properties / takeOver

Added value: +{
+  "description": "Only when the user says so: act even though another conversation is operating this screen, which then holds it no longer.",
+  "type": "boolean"
+}

AddedOct 8, 2026

TDQS

A3.9/5.0

Behavior5/5

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

Goes well past the annotations: it discloses that the result carries the new state plus the next snapshotId with no extra snapshot call, that a stale snapshot or human interaction aborts the action and returns current state for retry, and that a sent action is not proof of success. It also states the required ui and process permissions, which the annotations do not convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the action, then failure modes, then a caution, then permissions – a sensible ordering with essentially no filler. It is dense, packing four distinct facts into four sentences, but each fact is operationally useful rather than redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description carries the return-value burden and does so (new state + next snapshotId). The abort/retry contract and permission requirements round out a mutation tool whose annotations only say non-readonly, non-destructive. Minor gap: no mention of how the element is identified or of the decrement counterpart.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 60%; deviceId, takeOver and workSessionId are documented in-schema, while elementId (integer 1-600) and snapshotId (uuid) have no in-schema description. The description partially compensates by tying the action to 'the latest app_snapshot' and promising a next snapshotId, but never explains what elementId refers to, so the gap is only half closed.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource: 'Step a slider, stepper or other adjustable element of the latest app_snapshot up by one step.' The directional qualifier 'up by one' implicitly separates it from app_decrement without naming it, so an agent can distinguish the pair. Slightly short of 5 because the sibling app_decrement is never named and 'other adjustable element' leaves the target class a bit loose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage context is implied through preconditions (must operate on the latest snapshot, must not have intervening window changes or human input) rather than explicit 'use this when' guidance. It never states the alternative for stepping down (app_decrement) or when app_press/app_select would be preferable. An agent can infer the routing, but must do the inferring.

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

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