What is update-api-response-contract?

A guide for changing the data and formatting that an API sends back to callers, including fields, relationships, headers, status codes, and error responses.

Use it when changing shared API serialization, output formats, response headers, status handling, or error envelopes.

It helps keep response behavior consistent across endpoints while avoiding accidental exposure of sensitive fields.

update-api-response-contract — Skill by tarlepp/symfony-flex-backend

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add tarlepp/symfony-flex-backend --skill update-api-response-contract

Clone the repo

git clone --depth 1 https://github.com/tarlepp/symfony-flex-backend

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/tarlepp/symfony-flex-backend/update-api-response-contract/github.svg)](https://agentmods.dev/skills/tarlepp/symfony-flex-backend/update-api-response-contract)

Your own site

<a href="https://agentmods.dev/skills/tarlepp/symfony-flex-backend/update-api-response-contract"><img src="https://agentmods.dev/badge/skills/tarlepp/symfony-flex-backend/update-api-response-contract/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/tarlepp/symfony-flex-backend/update-api-response-contract"><img src="https://agentmods.dev/badge/skills/tarlepp/symfony-flex-backend/update-api-response-contract.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 31 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,950 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00031	$0.01950
Opus 5.5	$0.00012	$0.00780
Sonnet 5.5	$0.00006	$0.00390
Haiku 4.5	$0.00003	$0.00195

Measured 4d ago against content hash d8cc17afca95, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

update-api-response-contract scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/skills/update-api-response-contract/SKILL.md · 170 lines

How it starts

The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.

What is this?

Use this skill when changing response behavior shared across endpoints: serialization contexts and population groups, output formats, response headers, status handling, or error envelopes. For endpoint-specific behavior, also use add-custom-api-endpoint or add-rest-resource. For request DTOs and input mapping, use add-api-dto-mapping; an input DTO change does not automatically change response exposure.

Follow the shared skill guidance, including repository instructions and AI rules.

Table of Contents ᐞ

What is this
- Table of Contents

Response path map ᐞ

Inspect the affected producers and consumers before editing:

src/Rest/ResponseHandler.php and its interface: serializer context, format selection, status, content type, and serialization failures.
src/Rest/Traits/Methods/, RestMethodHelper, and RestResource: operation-specific data/status, exception conversion, associations, and resource serializer-context overrides.
src/Entity/ attributes and Set.* constants, including User and shared entity traits: actual serialized fields and relationship groups. Generic REST methods currently pass resource results to the serializer; do not assume request DTOs define their output or add a new response layer merely to change one field.
src/Controller/: custom response producers. Some use the response handler, others serialize with explicit groups and JsonResponse(json: true), and others return data directly through JsonResponse.
src/EventSubscriber/ResponseSubscriber.php and ExceptionSubscriber.php: API version header, exception status, logging, production-safe messages, and development-only debug details.
config/packages/framework.yaml, nelmio_cors.yaml, nelmio_api_doc.yaml, and config/services.yaml: serializer setup, browser-visible headers, documentation areas, and wiring.
tests/Integration/Rest/ResponseHandlerTest.php, response/exception subscriber tests in tests/Integration/EventSubscriber/ and tests/Unit/EventSubscriber/, plus affected HTTP tests in tests/E2E/Controller/: existing contract evidence and regression helpers.

Read the full file on GitHub · 170 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

4d ago First seen · 170 lines · 31 tokens per session scan A d8cc17afca95

Subscribe to this mod's changes

update-api-response-contract is a skill published in the GitHub repository tarlepp/symfony-flex-backend (288 stars, last pushed yesterday), licensed MIT. It adds 31 tokens to every session and 1,950 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-11-02.

Backend and APIs api flex rest rest-api symfony symfony-flex

update-api-response-contract next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
update-api-response-contracttarlepp/symfony-flex-backend	Skill	288	yesterday	MIT	A	31	Claude Code, Codex
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