Integration testing (MCP handshakes & tool contracts)
Exercise the seams where the model meets the rest of the system — tool and function contracts, MCP handshakes, retrieval calls, API auth — to catch connectivity and contract failures end to end.
Published June 26, 2026
How it works
Agentic and RAG systems are wiring as much as model. Integration tests drive the real seams: does the MCP handshake negotiate the tools you expect, do the advertised function schemas match what the model is actually told, does retrieval come back in the contracted shape, does auth and rate-limiting behave under load. These failures — schema mismatch, connectivity, access control, token and cost limits — are deterministic and reproducible, and they masquerade as model errors when left untested.
When to use it
Any system with tools, MCP servers, retrieval, or external APIs the model depends on; before and after every dependency or schema change.
Limitations
Covers the contract, not the judgement — a perfectly wired tool can still be called with hallucinated arguments. Verifies that the seams hold, not that the model uses them well.
Method yield
- Findings
- 2
- Versions spanned
- 5
- Yield score
- 7
Severity-weighted across the published findings below. Why we measure this →
Findings it surfaces (2)
Documented failures this method catches — the evidence it works.
- Hallucinated tool/function argumentsHigh
When calling tools, models invent argument values or call functions that weren't provided.
How it found it: A tool-contract test asserts every argument exists and matches the function schema, catching fabricated or mis-mapped values at the seam.
Tool use - Reasoning model regresses on tool use versus its base modelMedium
DeepSeek-R1 falls short of the base DeepSeek-V3 on function calling, multi-turn, complex role-play and JSON output — a reasoning-tuned model trading away tool-use reliability, later restored in R1-0528.
How it found it: A tool-contract test catches the weaker function-calling and JSON behavior at the seam.
Tool use
References & further reading
Cite this
Qlarify Labs. (2026). Integration testing (MCP handshakes & tool contracts). Retrieved from https://labs.qlarify.fi/methods/integration-testing