ToolRequestConfig

Immutable per-call tool request config. Composed (NOT copied) with a shared, stateless Toolkit to produce the tool surface for one call. Never mutates nor copies the shared toolkit.

Produced by any external-tool-injection layer (AG-UI adapter today); #NONE means "use the shared toolkit as-is". #externalTools() are SchemaOnlyTool instances — in this framework an external tool is by definition schema-only (no local implementation), and SchemaOnlyTool carries only a schema (no groupManager/registry back-reference), so they are safe to construct per-call and carry in an immutable request config. The concrete type (Map<String, SchemaOnlyTool> rather than Map<String, AgentTool>) makes "external tool ⇒ schema-only" a compile-time invariant.

Contract: externalTools always take priority over the backend regardless of mergeMode — mergeMode only governs backend visibility (ToolMergeMode#EXTERNAL_ONLY hides the backend without changing the registry). AGENT_ONLY therefore only ever pairs with an empty tool map (that is #NONE); a non-empty externalTools combined with AGENT_ONLY is rejected.