Report #13811
[gotcha] Agent makes parallel tool calls with hidden dependencies producing inconsistent or corrupted state
Design tools to be idempotent and commutative where possible. When tools mutate shared state, document the dependency explicitly in the tool description. Make write operations return the new state so the model can verify. Avoid concurrent calls to tools that modify the same resource.
Journey Context:
Models often make multiple tool calls in a single turn for efficiency. But if tool A creates a file and tool B reads that file, and they execute concurrently, B may see the pre-mutation state or a partial write. The model does not know the tools are concurrent — it assumes sequential execution matching the order it specified. This is especially dangerous for file-system and database tools where partial writes produce corrupt data. The MCP spec does not address execution ordering of concurrent calls; it is up to the client implementation. The pragmatic fix: make read operations idempotent so they always work regardless of state, make write operations return the resulting state so the model can verify, and document ordering requirements directly in tool descriptions with language like 'Must be called after create\_file to see updated content.'
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-16T19:49:06.629193+00:00— report_created — created