sigoden/aichat · error

Please enable function calling before using the agent.

Error message

Please enable function calling before using the agent.

What it means

Thrown by the agent-entry function in src/config/mod.rs:1495 when `config.read().function_calling` is false. Agents rely on function/tool calling to operate, so the library requires the global `function_calling` flag to be enabled before `Agent::init` is attempted. This is a preflight capability check, not a model-side failure.

Solutions

1. Enable function calling in the config (set the `function_calling` option to true) and retry
2. Switch to a model/provider that supports function calling
3. If function calling cannot be enabled, avoid agent mode and use plain chat/rag workflows

Example fix

// before (function_calling disabled)
config.use_agent("my-agent", None, signal).await?;
// after
if !config.read().function_calling {
    config.write().function_calling = true; // or fix the config file
}
config.use_agent("my-agent", None, signal).await?;

if !config.read().function_calling {
    bail!("Enable function calling in your config before using agents");
}

if let Err(e) = config.use_agent(name, session, signal).await {
    if e.to_string().contains("enable function calling") {
        eprintln!("Set function_calling=true (or switch to a tool-capable model)");
        return Ok(());
    }
    return Err(e.into());
}

When it happens

Trigger: Calling the agent entry function (CLI `.agent <name>` or its Rust wrapper) with a config where the `function_calling` option is disabled/unset — typically a model or provider config that lacks tool-calling support or has the flag explicitly off.

Common situations: Users on models/providers without function-calling support trying to use agents; configs migrated from older versions where the flag defaulted differently; users who disabled function calling globally for cost/compat reasons and forgot.

Related errors

• Invalid starter value
• Invalid document path
• No models
• Unknown client
• Unknown model

AI-assisted analysis of sigoden/aichat@82976d349a (2026-09-09). Data as JSON: /api/errors/00645965eff5bffa. Report an issue: GitHub.

Appendix: source

Thrown at src/config/mod.rs:1495

    pub fn rag_template(&self, embeddings: &str, text: &str) -> String {
        if embeddings.is_empty() {
            return text.to_string();
        }
        self.rag_template
            .as_deref()
            .unwrap_or(RAG_TEMPLATE)
            .replace("__CONTEXT__", embeddings)
            .replace("__INPUT__", text)
    }

    pub async fn use_agent(
        config: &GlobalConfig,
        agent_name: &str,
        session_name: Option<&str>,
        abort_signal: AbortSignal,
    ) -> Result<()> {
        if !config.read().function_calling {
            bail!("Please enable function calling before using the agent.");
        }
        if config.read().agent.is_some() {
            bail!("Already in a agent, please run '.exit agent' first to exit the current agent.");
        }
        let agent = Agent::init(config, agent_name, abort_signal).await?;
        let session = session_name.map(|v| v.to_string()).or_else(|| {
            if config.read().macro_flag {
                None
            } else {
                agent.agent_prelude().map(|v| v.to_string())
            }
        });
        config.write().rag = agent.rag();
        config.write().agent = Some(agent);
        if let Some(session) = session {
            config.write().use_session(Some(&session))?;
        } else {
            config.write().init_agent_shared_variables()?;

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