Tool-schema bias – Definition & Meaning

Definition of tool-schema bias

: systematic variation in an AI agent's performance caused by how functionally equivalent tools are named, grouped, structured, or presented in a tool schema rather than by any change in the actions the tools can perform
- The evaluation exposed tool-schema bias when the agent failed after several APIs were merged behind one dispatcher function.
- The team tested equivalent function definitions before deployment because tool-schema bias can differ from one model family to another.

Origin & history

first known use2026

The term was introduced in 2026 research on action-space shaping for language-model agents. The study compared verified-equivalent tool schemas and found that changing interface representation alone could substantially change agent success rates.

Editorial references

Sources & further reading

2 sources

Action-Space Shaping for LLM Agents: Measuring and Mitigating Tool-Schema Bias Research Preprint · arXiv · 2026-09-28
Tool-Schema Bias: Measure the Interface Before You Ship Independent Technical Analysis · AgentPatterns.ai · 2026-09-30

Test yourself

Which of these is the meaning of tool-schema bias?

Related terms

tool use a model's ability to call external tools, such as a search engine, calculator, code runner, or… function calling an API feature in which a model, instead of replying in plain text, outputs a structured… structured output model output that follows a fixed, machine-readable format such as JSON with specific fields… action space the complete set of actions an AI system is able or permitted to choose in an environment… MCP Model Context Protocol: an open standard for connecting AI applications to outside tools and… harness engineering the work of building everything around an AI model that lets it act as a reliable agent… eval a set of test cases used to measure how well a model or AI feature performs on the tasks you…

Cite this entry

"Tool-schema bias." AI Dictionary, Dadgogo, https://dadgogo.com/dictionary/tool-schema-bias/. Accessed 19 Oct. 2026.