Add API_POLICIES.md (closes #137)

prompts/API_POLICIES.md states sneak's rule from
sneak/routewatch#199: a value in an API
response is never a string with a label or unit in it. A native value
is sent as that type, with its unit in the field name.

The list at the top of REPO_POLICIES.md and the two code style
commands in the README now name the new file.

Model: opus-5-5

README.md

@@ -37,9 +37,9 @@ new repo file added, etc.)."
 **Code style and conventions:**
 
 ```bash
-claude "Read $TD/prompts/CODE_STYLEGUIDE.md and whichever
-language-specific styleguides in $TD/prompts/ apply to this repo
-(CODE_STYLEGUIDE_GO.md, CODE_STYLEGUIDE_JS.md, CODE_STYLEGUIDE_PYTHON.md,
+claude "Read $TD/prompts/CODE_STYLEGUIDE.md and whichever other
+documents in $TD/prompts/ apply to this repo (API_POLICIES.md,
+CODE_STYLEGUIDE_GO.md, CODE_STYLEGUIDE_JS.md, CODE_STYLEGUIDE_PYTHON.md,
 GO_HTTP_SERVER_CONVENTIONS.md). Then review the application code in this
 repo and bring it into compliance with those coding standards. Your scope
 is application code structure and style: naming, patterns, error
@@ -79,9 +79,9 @@ one for linter fixes, one for README, one for each new repo file, etc.)."
 **Code style and conventions:**
 
 ```bash
-claude "Read $TD/prompts/CODE_STYLEGUIDE.md and whichever
-language-specific styleguides in $TD/prompts/ apply to this repo
-(CODE_STYLEGUIDE_GO.md, CODE_STYLEGUIDE_JS.md, CODE_STYLEGUIDE_PYTHON.md,
+claude "Read $TD/prompts/CODE_STYLEGUIDE.md and whichever other
+documents in $TD/prompts/ apply to this repo (API_POLICIES.md,
+CODE_STYLEGUIDE_GO.md, CODE_STYLEGUIDE_JS.md, CODE_STYLEGUIDE_PYTHON.md,
 GO_HTTP_SERVER_CONVENTIONS.md). Then review the application code in this
 repo and bring it into compliance with those coding standards. Your scope
 is application code structure and style: naming, patterns, error

TODO.md

@@ -21,6 +21,11 @@ fmt-check, and commit.
 
 # Completed Steps
 
+- 2026-10-27: Added `prompts/API_POLICIES.md`
+  (https://git.eeqj.de/sneak/prompts/issues/137). It holds sneak's rule from
+  https://git.eeqj.de/sneak/routewatch/issues/199 that a value in an API
+  response is never a string with a label or unit in it. `REPO_POLICIES.md` and
+  the code style commands in the README name the new file.
 - 2026-10-21: Check builds may now also keep the Python packages a `test` phase
   installs from `Pipfile.lock` (issue 133), on sneak's ruling in
   https://git.eeqj.de/sneak/rfscan/issues/80#issuecomment-153437. The install

prompts/API_POLICIES.md

@@ -0,0 +1,20 @@
+---
+title: API Policies
+last_modified: 2026-10-27
+---
+
+A value in an API response is never a string with a label or unit in it. A value
+of a native type is sent as that type, and its unit goes in the field name, for
+example `_ms`.
+
+Wrong:
+
+```json
+{ "execution_time": "0 ms" }
+```
+
+Right:
+
+```json
+{ "execution_time_ms": 0 }
+```

prompts/REPO_POLICIES.md

@@ -1,6 +1,6 @@
 ---
 title: Repository Policies
-last_modified: 2026-10-26
+last_modified: 2026-10-27
 ---
 
 This document covers repository structure, tooling, and workflow standards. Code
@@ -12,6 +12,7 @@ style conventions are in separate documents:
 - [JavaScript](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/CODE_STYLEGUIDE_JS.md)
 - [Python](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/CODE_STYLEGUIDE_PYTHON.md)
 - [Go HTTP Server Conventions](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/GO_HTTP_SERVER_CONVENTIONS.md)
+- [API Policies](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/API_POLICIES.md)
 
 ---