An agent is only as useful as the actions it can take safely.
Why it matters
A model without tools can only talk. A production agent needs to read systems of record, call APIs, trigger workflows, and return evidence. MCP is one emerging standard for this boundary, but the deeper requirement is stable tool contracts with clear permissions and traceable results.
Build this
- Tool definitions with tight schemas, clear descriptions, and least-privilege credentials.
- A registry that separates read, write, destructive, and externally visible actions.
- MCP servers or adapter services that wrap real APIs without leaking implementation details.
- Tool result formatting that returns focused evidence instead of raw dumps.
Watch for
- Tools that accept free-form strings where structured inputs would work.
- One broad tool that can do everything instead of narrow tools with clear intent.
- Credentials available to the agent when the task does not need them.
- Tool results that are too large, too vague, or impossible to audit.
Proof it works
- Every tool call is logged with caller, input summary, output summary, latency, and permission decision.
- Dangerous tools require approval or a constrained sandbox.
- A failing integration returns a typed error the agent can recover from.
Implementation checklist
01
Start with read-only tools, then add write tools behind explicit approval gates.
02
Validate tool inputs and outputs at the integration boundary.
03
Return IDs, links, and short summaries so reviewers can inspect primary sources.
04
Keep MCP as a protocol choice, not the only design principle.