Implementation:Ollama Ollama Tools Parser

Knowledge Sources	Ollama
Domains	Tool Calling, Streaming Parser
Last Updated	2025-02-15 00:00 GMT

Overview

Implements a streaming parser that detects and extracts tool calls from model output, matching function names and arguments against a list of available tools.

Description

The Parser is a three-state machine (LookingForTag, ToolCalling, Done) that processes model output incrementally via the Add method. It buffers incoming text, searches for the tool call tag (extracted from the model's chat template), then enters tool calling mode. findTool matches tool names in the buffer with disambiguation for partial names. findArguments parses JSON objects from the buffer, searching for "arguments" or "parameters" fields within nested structures. For models using { or [ as tags, tool calling is only attempted if the first non-whitespace character matches. The parser returns both tool calls and content that should be sent to the user.

Usage

Used during chat completion responses when tools are provided in the request. The parser processes each token as it is generated by the model, accumulating text until a complete tool call is detected or the generation ends.

Code Reference

Source Location

• Repository: Ollama
• File: tools/tools.go
• Lines: 1-381

Signature

type Parser struct {
    // unexported fields: state, buffer, tag, tools, etc.
}

func GetBuffer(s string) string
func NewParser(tools []api.Tool, template string) *Parser
func NewParserWithTag(tools []api.Tool, tag string) *Parser
func (p *Parser) Add(s string) (string, []api.ToolCall, error)

Import

import "github.com/ollama/ollama/tools"

I/O Contract

Inputs

Name	Type	Required	Description
tools	[]api.Tool	Yes	List of available tools with their function names and parameter schemas
template	string	Yes	Chat template string used to extract the tool call tag
s	string	Yes	Incremental model output text to parse (Add method)

Outputs

Name	Type	Description
content	string	Text content to pass through to the user (not part of tool calls)
toolCalls	[]api.ToolCall	Detected tool calls with function name and arguments
error	error	Parsing error if tool call JSON is malformed

Usage Examples

// Create a parser with available tools
parser := tools.NewParser(requestTools, chatTemplate)

// Process model output token by token
for token := range modelOutput {
    content, toolCalls, err := parser.Add(token)
    if err != nil {
        // handle error
    }
    if content != "" {
        // send content to user
    }
    for _, tc := range toolCalls {
        // execute tool call: tc.Function.Name, tc.Function.Arguments
    }
}

Related Pages

• Principle:Ollama_Ollama_Tool_Call_Parsing