docs: make technical prose concrete

docs/cookbook/adding-a-tool.md

@@ -56,7 +56,7 @@ The producer supplies synchronous `cancel`, non-rejecting `done` that settles af
 
 ## Execution policy and observation
 
-Prefer not to build deployment policy into the tool. Use `tools/pre-execute` for extensible allow/deny/ask policy (the [permission-gate example](extension-cookbook.md#a-hook-plugin-permission-gate-example)), `ctx.tools.guard()` for a final monotonic deny that later listeners cannot undo, `tools/execute` to wrap canonical dispatch with a deadline/retry/metrics scope, `tools/post-execute` to replace either presentation content or the canonical value, block, or attach model-facing context, and `tools/result` to observe the immutable normalized outcome. A content replacement leaves programmatic access to `value` intact; confidentiality policy blocks or replaces the value. A sandboxing implementation can also sit behind the tool's executor capability seam; the exact contracts are in the [`dsh-tools` README](../../packages/core/tools/README.md#extension-points).
+Prefer not to build deployment policy into the tool. Use `tools/pre-execute` for extensible allow/deny/ask policy (the [permission-gate example](extension-cookbook.md#a-hook-plugin-permission-gate-example)), `ctx.tools.guard()` for a final monotonic deny that later listeners cannot undo, `tools/execute` to wrap dispatch with a deadline, retry, or metrics collection, `tools/post-execute` to replace presentation content or the returned value, block the result, or attach model-facing context, and `tools/result` to observe the immutable normalized outcome. A content replacement leaves programmatic access to `value` intact; confidentiality policy blocks or replaces the value. A sandboxing implementation can also run inside the tool's executor implementation; the [`dsh-tools` README](../../packages/core/tools/README.md#extension-points) defines each extension point's inputs, order, return values, and failure behavior.
 
 ## Code Mode reaches your tool for free
 
@@ -85,7 +85,7 @@ Hard rules (they bite if broken):
 
 - **Purity.** These run on live streaming AND on session-log REPLAY, so they must be pure functions of `args` (+ the result) — NO I/O, NO reading session state, NO clock/random. A diff is derived from the args (`write` uses `oldText: null` because a call-time presenter has no prior file content); the UI adapter, not the tool, supplies session context. If you find yourself wanting the file's old content or the working directory inside `presentCall`, stop — that belongs in durable result metadata or the adapter, not the presenter.
 - **UI-only formatting stays out of the model result.** A fenced ` ```console ` block, a diff, a relativized path—none of these belongs in the canonical value or Native content merely to serve a UI. `output.render` owns model-facing prose; `presentationMeta` plus the card presenters own replayable UI state. A `terminal` result view carries raw output and the adapter adds any fallback framing.
-- **`defineTool` soft-validates the display path.** A malformed/older logged arg shape makes the wrapper return `undefined` (a generic fallback) rather than throw — display must never crash a replay.
+- **`defineTool` soft-validates the display path.** Malformed or older logged arguments make the wrapper return `undefined` (a generic fallback) rather than throw — display must never crash a replay.
 
 The neutral vocabulary lives in `dsh-tools`; tools never import a UI or transport type. Host/client runtimes map each `card` into their own view. The design and the why are in [the render-intent-union Agent Note](../../.agents/notes/implemented/architecture/2026-07-02-tool-render-intent-union.md); `dsh-tool-fs` (generic/diff) and `dsh-tool-bash` (terminal) are the reference implementations.