fix: add tool_info schema discovery for WASM tools (#1086)

* fix: add tool_info schema discovery for WASM tools

* refactor: simplify WASM schema and hint state

* refactor: store tool_info registry reference as Weak

src/tools/builtin/mod.rs

@@ -15,6 +15,7 @@ pub mod secrets_tools;
 pub(crate) mod shell;
 pub mod skill_tools;
 mod time;
+mod tool_info;
 
 pub use echo::EchoTool;
 pub use extension_tools::{
@@ -39,6 +40,7 @@ pub use secrets_tools::{SecretDeleteTool, SecretListTool};
 pub use shell::ShellTool;
 pub use skill_tools::{SkillInstallTool, SkillListTool, SkillRemoveTool, SkillSearchTool};
 pub use time::TimeTool;
+pub use tool_info::ToolInfoTool;
 mod html_converter;
 pub mod image_analyze;
 pub mod image_edit;

src/tools/builtin/tool_info.rs

@@ -0,0 +1,183 @@
+//! On-demand tool discovery (like CLI `--help`).
+//!
+//! Two levels of detail:
+//! - Default: name, description, parameter names (compact ~150 bytes)
+//! - `include_schema: true`: adds the full typed JSON Schema
+//!
+//! Keeps the tools array compact (WASM tools use permissive schemas)
+//! while allowing precise discovery when needed.
+
+use std::sync::Weak;
+
+use async_trait::async_trait;
+
+use crate::context::JobContext;
+use crate::tools::registry::ToolRegistry;
+use crate::tools::tool::{Tool, ToolError, ToolOutput, require_str};
+
+pub struct ToolInfoTool {
+    registry: Weak<ToolRegistry>,
+}
+
+impl ToolInfoTool {
+    pub fn new(registry: Weak<ToolRegistry>) -> Self {
+        Self { registry }
+    }
+}
+
+#[async_trait]
+impl Tool for ToolInfoTool {
+    fn name(&self) -> &str {
+        "tool_info"
+    }
+
+    fn description(&self) -> &str {
+        "Get info about any tool: description and parameter names. \
+         Set include_schema to true for the full typed parameter schema."
+    }
+
+    fn parameters_schema(&self) -> serde_json::Value {
+        serde_json::json!({
+            "type": "object",
+            "properties": {
+                "name": {
+                    "type": "string",
+                    "description": "Name of the tool to get info about"
+                },
+                "include_schema": {
+                    "type": "boolean",
+                    "description": "If true, include the full typed JSON Schema for parameters (larger response). Default: false.",
+                    "default": false
+                }
+            },
+            "required": ["name"]
+        })
+    }
+
+    async fn execute(
+        &self,
+        params: serde_json::Value,
+        _ctx: &JobContext,
+    ) -> Result<ToolOutput, ToolError> {
+        let start = std::time::Instant::now();
+        let name = require_str(&params, "name")?;
+        let include_schema = params
+            .get("include_schema")
+            .and_then(|v| v.as_bool())
+            .unwrap_or(false);
+
+        let registry = self.registry.upgrade().ok_or_else(|| {
+            ToolError::ExecutionFailed(
+                "tool registry is no longer available for tool_info".to_string(),
+            )
+        })?;
+
+        let tool = registry.get(name).await.ok_or_else(|| {
+            ToolError::InvalidParameters(format!("No tool named '{name}' is registered"))
+        })?;
+
+        let schema = tool.discovery_schema();
+
+        // Extract just param names from the schema's "properties" keys
+        let param_names: Vec<&str> = schema
+            .get("properties")
+            .and_then(|p| p.as_object())
+            .map(|props| props.keys().map(|k| k.as_str()).collect())
+            .unwrap_or_default();
+
+        let mut info = serde_json::json!({
+            "name": tool.name(),
+            "description": tool.description(),
+            "parameters": param_names,
+        });
+
+        if include_schema {
+            info["schema"] = schema;
+        }
+
+        Ok(ToolOutput::success(info, start.elapsed()))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::tools::builtin::EchoTool;
+    use std::sync::Arc;
+
+    #[tokio::test]
+    async fn test_tool_info_default_returns_param_names() {
+        let registry = Arc::new(ToolRegistry::new());
+        registry.register(Arc::new(EchoTool)).await;
+
+        let tool = ToolInfoTool::new(Arc::downgrade(&registry));
+        let ctx = JobContext::default();
+        let result = tool
+            .execute(serde_json::json!({"name": "echo"}), &ctx)
+            .await
+            .unwrap();
+
+        let info = &result.result;
+        assert_eq!(info["name"], "echo");
+        assert!(!info["description"].as_str().unwrap().is_empty());
+        // Default: parameters is an array of names, not the full schema
+        assert!(info["parameters"].is_array());
+        assert!(
+            info["parameters"]
+                .as_array()
+                .unwrap()
+                .iter()
+                .any(|v| v.as_str() == Some("message")),
+            "echo tool should have 'message' parameter: {:?}",
+            info["parameters"]
+        );
+        // No schema field by default
+        assert!(info.get("schema").is_none());
+    }
+
+    #[tokio::test]
+    async fn test_tool_info_with_schema() {
+        let registry = Arc::new(ToolRegistry::new());
+        registry.register(Arc::new(EchoTool)).await;
+
+        let tool = ToolInfoTool::new(Arc::downgrade(&registry));
+        let ctx = JobContext::default();
+        let result = tool
+            .execute(
+                serde_json::json!({"name": "echo", "include_schema": true}),
+                &ctx,
+            )
+            .await
+            .unwrap();
+
+        let info = &result.result;
+        assert_eq!(info["name"], "echo");
+        // With include_schema: true, schema field should be present
+        assert!(info["schema"].is_object());
+        assert!(info["schema"]["properties"].is_object());
+    }
+
+    #[tokio::test]
+    async fn test_tool_info_unknown_tool() {
+        let registry = Arc::new(ToolRegistry::new());
+        let tool = ToolInfoTool::new(Arc::downgrade(&registry));
+        let ctx = JobContext::default();
+        let result = tool
+            .execute(serde_json::json!({"name": "nonexistent"}), &ctx)
+            .await;
+        assert!(result.is_err());
+    }
+
+    #[tokio::test]
+    async fn test_tool_info_registry_dropped() {
+        let registry = Arc::new(ToolRegistry::new());
+        let tool = ToolInfoTool::new(Arc::downgrade(&registry));
+        drop(registry);
+
+        let ctx = JobContext::default();
+        let result = tool
+            .execute(serde_json::json!({"name": "echo"}), &ctx)
+            .await;
+        assert!(matches!(result, Err(ToolError::ExecutionFailed(_))));
+    }
+}