What is TCC (Task–Call Contract)?
TCC (Task–Call Contract) is a task acceptance method proposed by LS-Labs: before testing, fix the task, the tool version and the correct behavior; after testing, check item by item the tool-selection decision, the arguments, the reading of the returned result and the state evidence.
It is an LS-Labs framework, not an industry-standard protocol or a model feature.
What T, C and C stand for
T is Task, the job the user actually wants done. The first C is Call, the tool and arguments the model proposes. The second C is Contract, the correct behavior and acceptance conditions agreed in advance.
The three terms describe relationships to check, not three stages that run in sequence. The contract first defines when to call, ask a follow-up question or stop, and then defines the correct arguments, the meaning of the result and the expected state.
Two acceptance dimensions, three check outcomes
“Task fit” checks which tool should be chosen and whether the model should ask a follow-up question or make no call. “Call and result” checks the arguments, the reading of the result and the execution state. Each item is recorded from observation as pass, fail or untested; when a required record is missing, the item stays untested.
For example, if a user only wants to check availability, the model may pick the right lookup tool and still fill in the wrong branch. Likewise, if the backend has created a reservation but the model never obtained verifiable evidence of completion, the call log alone cannot establish that the delegated task is done.
How TCC relates to TSO and AX
TSO breaks down how a tool is discovered, selected and called; TCC writes the expectation and the observation for a single task into a test card that can be rerun. AX goes further and looks at the agent's experience of using the whole product.
Tool descriptions and test cards cannot replace the backend's argument validation, authorization and state checks. The model proposing a call, the service actually executing it and the user's task being completed should be recorded separately.
Sources and scope
- LS-Labs (2026-11-05): Task–Call Contract v0.1 research notes (Traditional Chinese)
- LS-Labs (2026-11-05): Restaurant and invoice bilingual defect challenge research notes (Traditional Chinese)
Sources as checked for the source-language entry on 2026-11-06. This English edition is a translation: it adds no new claims and does not represent a new check of the sources.