FlowiseAI/Flowise · error · Error

This agent requires that the "bindTools()" method be…

Error message

This agent requires that the "bindTools()" method be implemented on the input model.

What it means

ToolAgent (the non-conversational variant) builds a tool-calling agent and requires the chat model to implement `bindTools()`. If `model.bindTools === undefined` it throws before constructing the RunnableSequence. Identical precondition to error 29, just in ToolAgent.

Solutions

1. Wire a tool-calling-capable chat model (ChatOpenAI gpt-4/3.5-turbo, ChatAnthropic, etc.).
2. Upgrade @langchain/core and the provider package.
3. Implement bindTools on custom model classes.
4. Confirm the model component is the tool-capable variant.

Example fix

// before
    if (model.bindTools === undefined) {
        throw new Error(`This agent requires that the "bindTools()" method be implemented on the input model.`)
    }
// after
    if (typeof model.bindTools !== 'function') {
        throw new Error(`Model "${model.constructor?.name ?? 'unknown'}" does not implement bindTools(). Use a tool-calling-capable chat model.`)
    }

if (typeof (model as any).bindTools !== 'function') {
  throw new Error('ToolAgent needs a tool-calling-capable model.')
}

const hasBindTools = (m: unknown): m is { bindTools: (tools: unknown[]) => unknown } =>
  typeof (m as any)?.bindTools === 'function'

try {
  const agent = await buildToolAgent(model, tools, ...)
} catch (e) {
  if ((e as Error).message.includes('bindTools()')) swapToToolCapableModel()
  throw e
}

When it happens

Trigger: Selected model lacks tool-calling support, or the installed LangChain version predates the bindTools interface. Common when reusing a plain/legacy chat model node.

Common situations: Switched models to one without function calling; downgraded @langchain/core; custom model class without bindTools; using an older Flowise chat-model component.

Related errors

• This agent requires that the "bindTools()" method be…
• Agent needs to have a function calling capable models.
• Tool not found.
• Agent name is required!
• Assistant not found

AI-assisted analysis of FlowiseAI/Flowise@abe4a8601a (2026-08-12). Data as JSON: /api/errors/3877d34b95325550. Report an issue: GitHub.

Appendix: source

Thrown at packages/components/nodes/agents/ToolAgent/ToolAgent.ts:333

                const lastMessage = prompt.promptMessages.pop() as HumanMessagePromptTemplate
                const template = (lastMessage.prompt as PromptTemplate).template as string
                const msg = HumanMessagePromptTemplate.fromTemplate([
                    ...messageContent,
                    {
                        text: template
                    }
                ])
                msg.inputVariables = lastMessage.inputVariables
                prompt.promptMessages.push(msg)
            }

            // Add the `agent_scratchpad` MessagePlaceHolder back
            prompt.promptMessages.push(messagePlaceholder)
        }
    }

    if (model.bindTools === undefined) {
        throw new Error(`This agent requires that the "bindTools()" method be implemented on the input model.`)
    }

    const modelWithTools = model.bindTools(tools)

    const runnableAgent = RunnableSequence.from([
        {
            [inputKey]: (i: { input: string; steps: ToolsAgentStep[] }) => i.input,
            agent_scratchpad: (i: { input: string; steps: ToolsAgentStep[] }) => formatToOpenAIToolMessages(i.steps),
            [memoryKey]: async (_: { input: string; steps: ToolsAgentStep[] }) => {
                const messages = (await memory.getChatMessages(flowObj?.sessionId, true, prependMessages)) as BaseMessage[]
                return messages ?? []
            },
            ...promptVariables
        },
        prompt,
        modelWithTools,
        new ToolCallingAgentOutputParser()
    ])

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