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. 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