Language Models Tools

Spice provides tools that help LLMs interact with the runtime. To specify these tools for a Spice model, include them in its params.tools.

For a list of available tools, or how to define additional tools, see Tool Components.

Tool Modes

The tools parameter on a model controls how tools are provided to the LLM:

Value	Description
auto	Automatically choose between direct tools and searchable registry discovery, excluding data sampling tools. When the number of available tools exceeds 20 and an embedding model is available, auto switches to registry-based discovery; otherwise it uses direct tools.
all	Provide all built-in and Spicepod-configured tools directly to the LLM.
search_registry	Use searchable registry discovery. The LLM receives tool_search and tool_invoke meta-tools instead of individual tool definitions. Requires an embedding model (see tool_embedding_model).
<tool1>, <tool2>, ...	Provide only the named tools directly.

Example: Specifying Tools for a Model

models:
  - name: sql-model
    from: openai:gpt-4o
    params:
      tools: list_datasets, sql, table_schema

Example: Using all default tools directly

models:
  - name: full-runtime
    from: openai:gpt-4o
    params:
      tools: all

Example: Using auto mode (default)

models:
  - name: full-runtime
    from: openai:gpt-4o
    params:
      tools: auto

For details on tool groups, see Tool Components.

Tool Registry

When the runtime exposes many tools (multiple MCP servers, lots of dataset-bound tools, or many Functions declared with as_tool: true), passing every tool definition into every chat turn consumes a large portion of the context window and degrades selection accuracy. The Tool Registry replaces individual tool definitions with two meta-tools — tool_search and tool_invoke — backed by a hybrid search index over the runtime's tool catalog. This typically saves ~10× the per-turn tool-definition tokens for tool-heavy Spicepods.

tools: auto enables the registry automatically when there are more than 20 tools and an embedding model is configured; tools: search_registry requires it.

See Tool Registry for the full reference, including the hybrid-search algorithm, tool_search / tool_invoke parameters and response shapes, and guidance on when to prefer direct tools.

Example: Specifying tools and tool groups

models:
  - name: full-runtime
    from: openai:gpt-4o
    params:
      tools: memory, sql

Tool Recursion Limit

When a model requests to call a runtime tool, Spice runs the tool internally and feeds the result back to the model. The model may then request another tool call based on the result, creating a chain of tool invocations. The tool_recursion_limit parameter limits the depth of this internal recursion. By default, this limit is set to 10.

Lowering the limit can help prevent runaway tool chains in cases where a model repeatedly invokes tools without converging on a final answer.

models:
  - name: my-model
    from: openai
    params:
      tool_recursion_limit: 3