tinyagents 1.0.0

//! Tool layer types used by the harness.
//!
//! These types define the call boundary every harness capability shares —
//! including sub-agents exposed as tools (see
//! [`crate::harness::subagent::SubAgentTool`]), which is how the recursive
//! architecture turns "agents calling agents" into ordinary tool calls.
//!
//! Here a [`ToolCall`] carries a required `id` so results can be correlated
//! back to the originating call, matching provider tool-call semantics.

use std::collections::HashMap;
use std::sync::Arc;

use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use serde_json::Value;

use crate::Result;
use crate::harness::context::RunContext;
use crate::harness::events::EventSink;
use crate::harness::ids::{RunId, ThreadId};

/// The model-visible syntax a tool declaration prefers.
///
/// Tool execution remains provider-neutral: after parsing, the harness invokes
/// tools with [`ToolCall::arguments`] as JSON so local schema validation,
/// middleware, tracing, and replay use one stable representation. This format
/// tells prompt renderers and provider adapters how a tool should be exposed to
/// a model when the provider does not force a native tool-calling shape.
#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", tag = "type")]
pub enum ToolFormat {
    /// Native JSON/function-call style. This is the default and maps directly to
    /// providers such as OpenAI Chat Completions.
    #[default]
    Json,
    /// XML tag style, for example
    /// `<search><query>rust</query></search>`.
    Xml,
    /// Parametric p-type style: a compact ordered-parameter call syntax such as
    /// `search("rust", 5)`.
    PType {
        /// Ordered parameter names used by compact renderers. The names should
        /// correspond to fields in [`ToolSchema::parameters`].
        parameters: Vec<String>,
    },
}

/// A model-visible declaration of a tool: its name, description,
/// JSON-schema-compatible parameter shape, and preferred tool-call format.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct ToolSchema {
    /// Canonical tool name (ASCII `snake_case` by convention).
    pub name: String,
    /// Human/model readable description of what the tool does.
    pub description: String,
    /// JSON Schema describing the model-visible input arguments.
    pub parameters: Value,
    /// Preferred model-visible tool-call format.
    #[serde(default, skip_serializing_if = "ToolFormat::is_json")]
    pub format: ToolFormat,
}

/// A request from the model to invoke a tool.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct ToolCall {
    /// Provider-assigned call id, required for result correlation.
    pub id: String,
    /// Name of the tool to invoke.
    pub name: String,
    /// Arguments supplied by the model, as raw JSON.
    #[serde(default)]
    pub arguments: Value,
}

/// The outcome of executing a [`ToolCall`].
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct ToolResult {
    /// Id of the [`ToolCall`] this result answers.
    pub call_id: String,
    /// Name of the tool that produced the result.
    pub name: String,
    /// Model-facing textual content.
    pub content: String,
    /// Optional structured value for application code.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub raw: Option<Value>,
    /// Error message when the tool failed; `None` on success.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub error: Option<String>,
    /// Wall-clock execution time in milliseconds.
    #[serde(default)]
    pub elapsed_ms: u64,
}

/// Live run context visible to a tool invoked by an agent loop.
///
/// The legacy [`Tool::call`] entry point remains available for direct calls and
/// tests. The agent loop uses [`Tool::call_with_context`] so recursive tools
/// such as sub-agents can inherit caller lineage while still isolating child
/// threads.
#[derive(Clone)]
pub struct ToolExecutionContext {
    /// Run that invoked the tool.
    pub run_id: RunId,
    /// Caller thread id, when the parent run is threaded.
    pub thread_id: Option<ThreadId>,
    /// Caller recursion depth.
    pub depth: usize,
    /// Maximum output tokens requested for each model turn in the caller's run.
    pub max_turn_output_tokens: Option<u32>,
    /// Shared event sink for nested run observability.
    pub events: EventSink,
}

impl ToolExecutionContext {
    /// Captures the non-generic tool-visible parts of a live [`RunContext`].
    pub fn from_run_context<Ctx>(ctx: &RunContext<Ctx>) -> Self {
        Self {
            run_id: ctx.config.run_id.clone(),
            thread_id: ctx.config.thread_id.clone(),
            depth: ctx.config.depth,
            max_turn_output_tokens: ctx.config.max_turn_output_tokens,
            events: ctx.events.clone(),
        }
    }
}

/// An incremental progress update emitted while a tool runs (streaming).
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct ToolDelta {
    /// Id of the [`ToolCall`] this delta belongs to.
    pub call_id: String,
    /// Incremental content fragment.
    pub content: String,
}

/// A tool the harness can invoke during an agent loop.
///
/// Generic over the application `State` so tools can read shared context
/// without exposing it to model-visible schemas.
#[async_trait]
pub trait Tool<State: Send + Sync>: Send + Sync {
    /// Canonical tool name.
    fn name(&self) -> &str;

    /// Human/model readable description.
    fn description(&self) -> &str;

    /// Returns the model-visible schema for this tool.
    fn schema(&self) -> ToolSchema;

    /// Executes the tool against application state and a validated call.
    async fn call(&self, state: &State, call: ToolCall) -> Result<ToolResult>;

    /// Executes the tool with access to caller run context.
    ///
    /// Implementors that do not need caller lineage can rely on the default,
    /// which delegates to [`Self::call`].
    async fn call_with_context(
        &self,
        state: &State,
        call: ToolCall,
        context: ToolExecutionContext,
    ) -> Result<ToolResult> {
        let _ = context;
        self.call(state, call).await
    }
}

/// A name-keyed registry of tools available to the harness.
pub struct ToolRegistry<State> {
    pub(crate) tools: HashMap<String, Arc<dyn Tool<State>>>,
}