Glossary

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Glossary / Evaluation and implementation guide

Tool Calling

Tool calling is the mechanism by which a model invokes external functions and APIs during a response.

The model emits a structured request naming a tool and its arguments, the platform executes the call, and the result returns to the model to continue.

This is the model-side invocation mechanism; Function Calling, a closely related term, emphasizes the schema contract that defines each tool's parameters.

For buyers, tool calling breadth and reliability determine whether an agent can actually act in your stack or only talk about acting.

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A practical example

Label: example. When a user asks 'what changed in the Acme pipeline this week?', the model issues a tool call to your CRM's deal-history endpoint with account and date arguments, then summarizes the returned data.

What to evaluate before investing

  • Ask which tool types the platform supports natively: REST APIs, databases, file systems, or custom code functions.
  • Test error paths: what does the model do when a tool returns an error, times out, or returns unexpected formats?
  • Check whether tool call arguments are validated before execution to prevent malformed requests hitting your systems.

Limitations and tradeoffs

Tool calling gives models direct reach into your systems; a hallucinated tool name or argument can trigger real API calls, so validation and allowlists are essential.

Plan your next step with MeshLine

Connect this decision to your automation, organic marketing and customer lifecycle management. In a MeshLine demo, discuss your existing tools, the scope you need and how to measure the result.

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