Documentation Index
Fetch the complete documentation index at: https://platform.stepfun.ai/docs/llms.txt
Use this file to discover all available pages before exploring further.
Toolcall (Function Calling) is an advanced capability on the StepFun platform. It lets models decide which external tools or functions to invoke to satisfy a user request. By using the Toolcall API, you can extend model capabilities to cover more use cases and offer richer features. Below is a minimal JSON request example that must include three key parameters:
{
"model": "step-1-8k",
"messages": [
{
"role": "user",
"content": "Hey, can you calculate (80 + 20) / 5 for me?"
}
],
"tools": [
{
"type": "function",
"function": {
"name": "Calculator",
"description": "This StepFun API provides basic arithmetic: addition, subtraction, multiplication, and division.",
"parameters": {
"properties": {
"formula": {
"type": "string",
"description": "Expression to evaluate. Only integers are supported. Operators: +, -, *, /, and parentheses. Example: (1 + 2) * 3."
}
},
"type": "object"
}
}
}
]
}
model: model name
The following models support Toolcall requests:
- step-1-8k
- step-1-32k
- step-1v-8k
- step-1v-32k
StepFun provides these built-in tools; configure them to enable the capability directly:
- Web search: call a search engine to fetch the latest information.
- Knowledge base search: upload text to a knowledge base and search it to reduce hallucinations.
Use tools to describe the functions available locally. Up to 128 tools are allowed. Each entry has type function and contains a function object with the name, description, and parameters.
name: letters, numbers, -, _; ideally under 64 characters. Use a clear English name so the model understands it (regex guideline: ^[a-zA-Z*][a-zA-Z0-9-_]63$).parameters: root type must be object. The content follows a subset of JSON Schema; keys follow the same naming rule. See JSON Schema for supported type values. description explains each parameter.description: explains what the function does so the model can choose it; English or Chinese is supported.
messages: conversation context
See Chat Completion request object.
Examples
from openai import OpenAI
client = OpenAI(api_key="STEP_API_KEY", base_url="https://api.stepfun.ai/v1")
completion = client.chat.completions.create(
model="step-1-8k",
messages=[
{
"role": "user",
"content": "Can you calculate (80 + 20) / 5 for me?"
}
],
tools=[
{
"type": "function",
"function": {
"name": "Calculator",
"description": "This StepFun API provides basic arithmetic: addition, subtraction, multiplication, and division.",
"parameters": {
"type": "object",
"properties": {
"formula": {
"type": "string",
"description": "Expression to evaluate. Only integers are supported. Operators: +, -, *, /, and parentheses. Example: '(1 + 2) * 3'."
}
}
}
}
}
]
)
print(completion)
import OpenAI from "openai";
const openai = new OpenAI({
apiKey: "STEP_API_KEY",
baseURL: "https://api.stepfun.ai/v1"
});
async function main() {
const completion = await openai.chat.completions.create({
model: "step-1-8k",
messages: [
{
role: "user",
content: "Can you calculate (80 + 20) / 5 for me?"
}
],
tools: [
{
type: "function",
function: {
name: "Calculator",
description: "This StepFun API provides basic arithmetic: addition, subtraction, multiplication, and division.",
parameters: {
type: "object",
properties: {
formula: {
type: "string",
description: "Expression to evaluate. Only integers are supported. Operators: +, -, *, /, and parentheses. Example: '(1 + 2) * 3'."
}
}
}
}
}
]
});
console.log(JSON.stringify(completion));
}
main();
curl https://api.stepfun.ai/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $STEP_API_KEY" \
-d '{
"model": "step-1-8k",
"messages": [
{
"role": "user",
"content": "Can you calculate (80 + 20) / 5 for me?"
}
],
"tools": [
{
"type": "function",
"function": {
"name": "Calculator",
"description": "This StepFun API provides basic arithmetic: addition, subtraction, multiplication, and division.",
"parameters": {
"type": "object",
"properties": {
"formula": {
"type": "string",
"description": "Expression to evaluate. Only integers are supported. Operators: +, -, *, /, and parentheses. Example: (1 + 2) * 3."
}
}
}
}
}
]
}'
{
"id": "b7b56af0-52a6-483f-a589-948182676a1b",
"object": "chat.completion",
"created": 1717744611,
"model": "step-1-8k",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "",
"tool_calls": [
{
"id": "call_ybVBO_JASgipgJH8xWbhKg",
"type": "function",
"function": {
"name": "Calculator",
"arguments": "{\"formula\": \"(80 + 20) / 5\"}"
}
}
]
},
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 151,
"completion_tokens": 25,
"total_tokens": 176
}
}
