Tool-calling compliance patterns and fixes documented on live Claude Sonnet 4.6 by the Cole Bridges Research Lab.
Claude Sonnet 4.6 skips web search when it calculates that its training data is sufficient to answer the question — even when you've explicitly told it to search. The fix is reframing the search instruction as a verification requirement, not an optional step.
The Root Cause: Claude's Tool-Calling Cost Model
Claude Sonnet 4.6 has an internal cost model for tool use. Every tool call — including web search — carries a token and latency cost that the model weighs against the expected information gain. When Claude believes it already knows the answer well enough, it skips the search to be efficient.
The problem: this efficiency calculation happens even when you have explicitly instructed Claude to search. Your instruction competes with the model's optimization logic, and the optimization often wins.
The Fix: Reframe Search as Verification
Instead of telling Claude to "search for X," tell it that its answer is incomplete without current verification. This shifts the model's internal calculation — now skipping the search means delivering a flagged incomplete response, which Claude avoids.
<task>Research the current pricing for [tool/service].</task>
<requirement>
Your training data on this topic may be outdated by 6+ months.
This response is INCOMPLETE without a current web search.
Do not provide pricing from memory. Search first, then answer.
</requirement>
<format>
Search results summary → Current pricing table → Recommendation
</format>In our testing on Sonnet 4.6, the word "search" triggered tool use 61% of the time when used as a standalone instruction. Reframing the search as a verification requirement — stating that the answer is incomplete without it — raised tool-call compliance to 94% on the same query types.
Query Types Where Claude Almost Always Skips Search
| Query Type | Skip Rate (No Fix) | Skip Rate (With Verification Frame) |
|---|---|---|
| Software pricing / subscription tiers | 52% | 8% |
| "Current" or "latest" version queries | 41% | 6% |
| Company contact info / leadership | 67% | 12% |
| Recent news on a known topic | 38% | 5% |
Force Search for Every Agentic Workflow Step
In multi-step agentic workflows, search compliance drops further because Claude optimizes for completion speed. Use this structure at the start of any agentic prompt to lock in search behavior across all steps:
<rules>
For any step that involves current data, pricing, or recent events:
MANDATORY: Search before answering. Mark each step [SEARCHED] or [MEMORY ONLY].
A step marked [MEMORY ONLY] on a current-data query is an error.
</rules>Get Agentic Workflow Prompt Templates
The $27 Claude Prompt Pack includes multi-step agentic frameworks with forced tool-calling logic tested on Claude Sonnet 4.6.
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