Topic starter
25/10/2026 11:03 am
TL;DR: Tool-selection accuracy in MCP agents drops sharply once a single context passes roughly 40 tools, because models begin matching on the first plausible name rather than fit, according to Archestra. The practical answer is to design a smaller tool surface with role scoping, identity scoping, and search-and-run patterns.
Editorial analysis by NHI Mgmt Group, based on content published by Archestra: “How many MCP tools is too many?”.
Key questions
Q: What breaks when agents are given too many MCP tools at once?
A: Agents can lose the ability to choose the right tool cleanly, especially when tool definitions, parameters, and response formats all enter the prompt at once.
Q: Why does tool sprawl increase operational risk for agentic systems?
A: Because every extra tool increases the number of actions the model can plausibly take, and that expands both error rates and the blast radius of a mistaken choice.
Q: How can security teams reduce MCP tool-selection errors?
A: Start by narrowing what the agent can see.
Practitioner guidance
- Cap the number of tools in any one agent context Set a hard threshold for visible tools per agent and treat large manifests as a design defect, not an acceptable default.
- Split broad agents by role and task Break general-purpose assistants into narrower agents so each one sees only the tools needed for its job, such as support, finance, or engineering.
- Rewrite tool descriptions for disambiguation Remove near-duplicate language from tool names and descriptions so the model can distinguish similar actions without guessing.
Bottom line: Too many MCP tools create a selection problem that looks like model weakness but is usually a manifest design issue.
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