Agent Tools vs MCP Tools
A local agent tool is typically a function registered directly with the runtime. An MCP tool is exposed by an MCP server and reached through a protocol boundary. Both can appear to the model as callable tools, but their operational characteristics differ.
| Area | Local tool | MCP tool |
|---|---|---|
| Execution | Inside app/runtime | External server/process |
| Discovery | Usually static code | Protocol discovery |
| Reuse across hosts | Often low | Primary benefit |
| Latency | Usually lower | May include process/network hop |
Use local tools when
The capability is tightly coupled to your app, cheap to execute in-process, or unlikely to be reused.
Use MCP when
The capability deserves a reusable service/process boundary, should work across hosts, or needs independent deployment and governance.