Many agent demos look impressive because the model selects a tool and returns a structured result. In production, a wrong date, an extra zero, a duplicate retry or an ambiguous timeout can create real damage. Reliability comes from boundary design, not from a reminder to “use tools carefully.”
1. The short answer
Define tools like backend API contracts: fields, types, enums, permission scope, return states and failure reasons. Do not leave “other information” as a free-form string. Validate dates, amounts, user IDs and external URLs again on the server.
2. The context
Split execution into planning, preview, execution and confirmation. Read-only tools can run automatically; low-risk writes can produce a change preview; sending, publishing, deleting and paying require explicit authorization. The model proposes a plan while the server owns side effects.
3. The real trade-offs
Timeouts and retries are where many systems fail. A timeout may mean the provider succeeded or never ran. Use idempotency keys, a status endpoint and backoff rather than blindly sending the request again. Every tool should expose an execution ID.
4. How to put it into practice
Test missing fields, denied permissions, empty results, duplicates, malicious instructions, provider outages and partial success. Measure parameter accuracy, duplicate calls, human takeover, rollback success and final task completion rather than only whether the model selected the right tool.
5. Common failure modes
Exposing many ungoverned APIs does not make an agent more capable. It expands the choice space and the blast radius. Start with one narrow workflow, stabilize logs and failure cases, then add tools one at a time.
6. FDE perspective
The goal is not valid JSON; it is a safe, traceable and recoverable business action. The model can plan and orchestrate, but contracts, permissions, idempotency, audit and rollback belong to the platform layer.
A practical checklist before shipping or buying
- Validate schemas and permissions on the server for every write tool.
- Preview, confirm and audit high-impact actions.
- Use idempotency and status queries for retries.
- Measure duplicate calls and rollback success.
What to do next
Start with one read-only workflow and add draft and confirmed execution stages gradually.
This article is based on public documentation and research from OpenAI function calling guide. The FDE perspective is editorial analysis, not a quotation from the source.
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