Connect LLMs to external tools — databases, APIs, payment systems. The model decides when to call a function and with what arguments.
Basic function calling
response = client.chat.completions.create(
model="forii/deepseek-v3",
messages=[{
"role": "user",
"content": "What's the GST rate for textiles?"
}],
tools=[{
"type": "function",
"function": {
"name": "lookup_gst_rate",
"description": "Look up GST rate for a product category",
"parameters": {
"type": "object",
"properties": {
"category": {
"type": "string",
"description": "Product category"
}
},
"required": ["category"]
}
}
}],
tool_choice="auto"
)
# Model returns tool_calls instead of text
tool_call = response.choices[0].message.tool_calls[0]
print(tool_call.function.name) # "lookup_gst_rate"
print(tool_call.function.arguments) # '{"category": "textiles"}'
const response = await client.chat.completions.create({
model: "forii/deepseek-v3",
messages: [{
role: "user",
content: "What's the GST rate for textiles?"
}],
tools: [{
type: "function",
function: {
name: "lookup_gst_rate",
description: "Look up GST rate for a product category",
parameters: {
type: "object",
properties: {
category: {
type: "string",
description: "Product category"
}
},
required: ["category"]
}
}
}],
tool_choice: "auto"
});
const toolCall = response.choices[0].message.tool_calls[0];
console.log(toolCall.function.name); // "lookup_gst_rate"
console.log(toolCall.function.arguments); // '{"category": "textiles"}'
curl https://api.forii.in/inference/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $FORII_API_KEY" \
-d '{
"model": "forii/deepseek-v3",
"messages": [{"role": "user", "content": "What'\''s the GST rate for textiles?"}],
"tools": [{
"type": "function",
"function": {
"name": "lookup_gst_rate",
"description": "Look up GST rate for a product category",
"parameters": {
"type": "object",
"properties": {
"category": {"type": "string", "description": "Product category"}
},
"required": ["category"]
}
}
}],
"tool_choice": "auto"
}'
Response
{
"choices": [{
"message": {
"role": "assistant",
"content": null,
"tool_calls": [{
"id": "call_forii_abc123",
"type": "function",
"function": {
"name": "lookup_gst_rate",
"arguments": "{\"category\": \"textiles\"}"
}
}]
},
"finish_reason": "tool_calls"
}]
}
# 1. Model requests a tool call
tool_call = response.choices[0].message.tool_calls[0]
# 2. You execute the function locally
result = lookup_gst_rate(category="textiles") # → {"rate": "5%"}
# 3. Send the result back to the model
followup = client.chat.completions.create(
model="forii/deepseek-v3",
messages=[
{"role": "user", "content": "What's the GST rate for textiles?"},
response.choices[0].message, # assistant message with tool_calls
{
"role": "tool",
"tool_call_id": tool_call.id,
"content": json.dumps(result) # your function result
}
]
)
print(followup.choices[0].message.content)
# "The GST rate for textiles is 5%."
| Value | Behavior |
|---|
"auto" | Model decides whether to call a tool (default) |
"none" | Model never calls a tool |
"required" | Model must call a tool |
{"type": "function", "function": {"name": "..."}} | Force a specific function |
response = client.chat.completions.create(
model="forii/deepseek-v3",
messages=[{"role": "user", "content": "Look up GST for both textiles and electronics"}],
tools=tools,
tool_choice="auto",
parallel_tool_calls=True, # default is True
)
India-specific tools that work with function calling: UPI payment status, Aadhaar verification, IRCTC train lookup, GST calculation, PAN validation. These aren’t built into Forii — they’re external tools your agent calls.
Parameters
| Parameter | Type | Description |
|---|
tools | array | Function/tool definitions |
tool_choice | string | object | auto, none, required, or {"type": "function", "name": "..."} |
parallel_tool_calls | boolean | Enable parallel function calls (default: true) |
