sync_assert_cross
Cross-device assertion: perform action on source device, verify result on target device with retries.
This record as markdown: /tools/alexgladkov-claude-in-mobile/sync-assert-cross.md
What sync_assert_cross does on Claude Mobile
AI agents invoke sync_assert_cross to trigger actions in Claude Mobile. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
Why sync_assert_cross is rated High
This tool executes actions on a source device and checks outcomes on a target device, spanning real device automation with potential side effects depending on what actions are performed. Since it drives UI interactions and app management on physical/simulated devices, it falls under Execute. The cross-device nature and retry logic amplify the blast radius if misused by an AI agent, warranting high severity.
From the tool's definition 'perform action on source device, verify result on target device with retries' — triggers actions across mobile devices (Android/iOS) and verifies cross-device results
Attacks that exploit this kind of access
The rule that runs sync_assert_cross safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Claude Mobile, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For sync_assert_cross, this is the rule to start with:
sync_assert_cross stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Claude Mobile, apply this rule, and every sync_assert_cross call is checked against it from then on.
Questions about sync_assert_cross
Cross-device assertion: perform action on source device, verify result on target device with retries. It is categorised as a Execute tool in the Claude Mobile MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Claude Mobile MCP server in PolicyLayer and add a rule for sync_assert_cross: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Claude Mobile. Nothing to install.
sync_assert_cross is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the sync_assert_cross rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for sync_assert_cross. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
sync_assert_cross is provided by the Claude Mobile MCP server (alexgladkov/claude-in-mobile). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
More on Claude Mobile, and thousands of servers like it.
Across the catalogue