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MCP Tool Contract Testing Skill

Validate MCP server tools with contract-style tests to catch schema drift, unsafe behavior, and integration regressions early.

by JSONbored·added 2026-04-10·
Claude CodeCodexWindsurfGeminiCursorCLI
HarnessClaude CodeCodexWindsurfGeminiCursorCLI
Level:advancedType:generalVerified:draft
Review first — review before installing

Open the source and read safety notes before installing.

Citation facts

Source-backed facts for citing this resource, derived directly from the registry — also available as plain text for AI assistants.

Canonical URL
https://heyclau.de/entry/skills/mcp-tool-contract-testing
Source URLs
https://modelcontextprotocol.io/specification/2025-06-18/, https://github.com/JSONbored/awesome-claude/blob/main/content/skills/mcp-tool-contract-testing.mdx
Package URL
/downloads/skills/mcp-tool-contract-testing.zip
Package SHA256
7e8f76baf26241e849bdb0108bf57628864ffb91a056e3878de27247f1d7d352
Safety notes
Use this skill as planning or review guidance; verify generated commands, code, configuration, and infrastructure changes before running them., Apply least-privilege credentials and test in staging or a disposable branch before using it on production systems, CI, deployment, or account-write workflows.
Privacy notes
Inputs can include source files, prompts, logs, account metadata, repository details, and operational context that may be sent to the configured AI model., Redact secrets, customer data, private URLs, credentials, and proprietary implementation details before sharing prompts, reports, or generated artifacts.
Platform compatibility
claude-code (native-skill), codex (native-skill), windsurf (native-skill), gemini (native-skill), cursor (adapter), cli (manual-context)
Author
JSONbored
Claim status
unclaimed
Last verified
2026-04-10

Decision playbook

Ready to evaluate for your workflow

Signals are comparatively strong, but you should still validate source, privacy posture, and package provenance for your environment.

Compare context
Selected

0

Current score

96

Baseline

—

Delta

No baseline selected

No major trust-signal divergence detected in the current selection.

Source and provenance checks

Complete

Confirm ownership and provenance before trusting install instructions.

  • Source link availableRequired

    Open the canonical repository and verify ownership.

    Done

  • Source provenance statusRequired

    Marked as first-party.

    Done

  • Metadata reviewed

    Registry metadata indicates a reviewed listing.

    Done

Safety and privacy checks

Complete

Validate risk disclosures before installation or API wiring.

  • Safety notes presentRequired

    Review the listed safety guidance before running commands.

    Done

  • Privacy notes presentRequired

    Review data handling notes before connecting accounts or secrets.

    Done

  • Trust level risk gateRequired

    Trust level does not block evaluation.

    Done

Package and install checks

Complete

Check package metadata and artifact integrity signals.

  • Install payload available

    Install or copy payload is available for review.

    Done

  • Package verification flag

    Package marked verified.

    Done

  • Checksum metadata

    SHA-256 hash is present.

    Done

Compare-driven decision checks

Needs review

Use compare context to validate trade-offs before adoption.

  • Compare tray has multiple entries

    Add at least one more entry to compare trust differences.

    Pending

  • Baseline comparison available

    No baseline peer selected yet.

    Pending

  • Diverging trust signals identified

    No major trust-signal divergence found.

    Pending

Setup at a glance

Package install

Copy-ready — paste the snippet to get started.

Install command

Provided

Config snippet

Not provided

Copy snippet

Provided

Prerequisites

3 to clear

Platforms

6 listed

Difficulty

77/100

Adoption plan

Balanced adoption plan

Current risk score 0/100. Use staged verification before broader rollout.

Risk 0

Pre-adoption checks

Validate source and review signals before any execution.

  • Confirm source provenanceRequired

    Source URL/provenance metadata is present.

    Done

  • Confirm metadata review state

    Listing has review metadata.

    Done

  • Verify install payload

    Install/config payload exists and can be inspected.

    Done

Security checks

Confirm safety, privacy, and package integrity signals.

  • Review safety notesRequired

    Safety notes are present.

    Done

  • Review privacy notesRequired

    Privacy notes are present.

    Done

  • Verify package integrity metadata

    Package verification/checksum metadata is available.

    Done

Rollout

Adopt in controlled steps based on the selected plan.

  • Run in isolated sandbox firstRequired

    Use a constrained sandbox and observe behavior across multiple tasks.

    Pending

  • Roll out graduallyRequired

    Roll out to a small cohort before wider usage.

    Pending

  • Set monitoring and fallback

    Define rollback path and monitor errors after adoption.

    Pending

Evidence readiness

Evidence readiness matrix · balanced

Required evidence gates are covered (6/6 signals complete).

Risk 0

Source provenance

Present

Source repository/provenance is listed.

Required in this preset

Metadata review

Present

Review metadata is present.

Required in this preset

Safety notes

Present

Safety notes are present.

Required in this preset

Privacy notes

Present

Privacy notes are present.

Optional in this preset

Package integrity

Present

Package integrity metadata is present.

Optional in this preset

Install payload

Present

Install payload is available.

Required in this preset

Required evidence gates are covered for this preset.

Decision timeline

Decision timeline · balanced

6/6 steps complete with no blocking gaps for this preset.

Risk 0

triage

Confirm source provenanceRequired

Source/provenance metadata is available.

Done

triage

Check metadata review statusRequired

Review metadata is available.

Done

verify

Review safety notesRequired

Safety notes are available.

Done

verify

Review privacy notes

Privacy notes are available.

Done

verify

Validate package integrity metadata

Package integrity metadata is available.

Done

rollout

Verify install payload and commandsRequired

Install payload is available.

Done

No required blockers for this timeline preset.

Prerequisite readiness

Prerequisite readiness

3 prerequisites to line up before setup.

0/3 ready
General3

Safety & privacy surface

Safety & privacy surface

2 safety and 2 privacy notes across 3 risk areas. Review closely: credentials & tokens, third-party handling.

3 areas
  • SafetyExecution & processesUse this skill as planning or review guidance; verify generated commands, code, configuration, and infrastructure changes before running them.
  • SafetyCredentials & tokensApply least-privilege credentials and test in staging or a disposable branch before using it on production systems, CI, deployment, or account-write workflows.
  • PrivacyThird-party handlingInputs can include source files, prompts, logs, account metadata, repository details, and operational context that may be sent to the configured AI model.
  • PrivacyCredentials & tokensRedact secrets, customer data, private URLs, credentials, and proprietary implementation details before sharing prompts, reports, or generated artifacts.

Safety notes

  • Use this skill as planning or review guidance; verify generated commands, code, configuration, and infrastructure changes before running them.
  • Apply least-privilege credentials and test in staging or a disposable branch before using it on production systems, CI, deployment, or account-write workflows.

Privacy notes

  • Inputs can include source files, prompts, logs, account metadata, repository details, and operational context that may be sent to the configured AI model.
  • Redact secrets, customer data, private URLs, credentials, and proprietary implementation details before sharing prompts, reports, or generated artifacts.

Prerequisites

  • MCP server implementation and tool catalog
  • Staging environment for test execution
  • Known expected outputs per critical tool

Schema details

Install type
package
Reading time
6 min
Difficulty score
77
Troubleshooting
Yes
Breaking changes
No
Package metadata
Package verified
Yes
SHA-256
7e8f76baf26241e849bdb0108bf57628864ffb91a056e3878de27247f1d7d352
Skill and platform metadata
Skill type
general
Skill level
advanced
Verification
draft
Verified at
2026-04-10
Retrieval sources
https://modelcontextprotocol.io/specification/2025-06-18/
Tested platforms
ClaudeCodexOpenClawCursorWindsurfGemini
PlatformSupportInstall path
claude-codeNative.claude/skills/<skill-name>/SKILL.md
codexNative.agents/skills/<skill-name>/SKILL.md
windsurfNative.windsurf/skills/<skill-name>/SKILL.md
geminiNative.gemini/skills/<skill-name>/SKILL.md or .agents/skills/<skill-name>/SKILL.md
cursorAdapter.cursor/rules/<skill-name>.mdc
cliManualAGENTS.md or tool-specific context file
Full copyable content
# Trigger
"Run the MCP tool contract testing skill on this server update."

# Required output
1) Tool contract matrix
2) Positive/negative test cases
3) Schema compliance report
4) Release go/no-go summary

About this resource

Overview

This skill helps AI agents enforce explicit behavior contracts for MCP tools. It prevents accidental schema drift, unsafe edge-case handling, and hidden regressions when tools evolve.

Compatibility

Native

  • Claude Code / Claude: native skill usage via SKILL.md.
  • Codex/OpenAI workflows: compatible with Agent Skills-style SKILL.md content as reusable workflow instructions.

Manual Adaptation

  • Gemini CLI: native skill usage via .gemini/skills/<skill-name>/SKILL.md or .agents/skills/<skill-name>/SKILL.md where supported.
  • Cursor: use the generated .cursor/rules/*.mdc adapter for project rules.
  • OpenClaw and similar agents: use the same skill content as a reusable prompt/workflow file when native skill import is unavailable.

Prerequisites

  • Contract definitions for high-value tools
  • Stable test inputs and expected outputs
  • Regression thresholds for release decisions

What This Skill Delivers

  • Contract catalog for each tool endpoint
  • Validation suite for payload and response guarantees
  • Safety/negative tests for malformed and adversarial inputs
  • Regression summary for release gating

How to Use This Skill

  1. Define mandatory response fields and allowed ranges.
  2. Build positive and negative test vectors.
  3. Execute against baseline and candidate builds.
  4. Compare behavior and schema diffs.
  5. Block release when contract-critical checks fail.

Troubleshooting

Issue: Tool output changes break downstream clients
Fix: Add strict backward-compatibility contract checks for public fields.

Issue: Tests pass but runtime still fails on edge cases
Fix: Add adversarial input suites and timeout/error propagation checks.

Issue: Frequent false positives in test suite
Fix: Split deterministic contract checks from heuristic quality checks.

Knowledge Freshness

Treat tooling details as time-sensitive. Re-validate APIs, limits, pricing, auth models, and deployment flags immediately before implementation. If docs conflict with prior memory, follow current official docs and release notes.

Retrieval Sources

Output Contract

  1. Return a concrete plan with implementation order.
  2. Provide production-ready commands/config/code snippets (not placeholders).
  3. Include explicit assumptions and unresolved risks.
  4. Include a verification checklist with pass/fail criteria.

Quality Gates

  • All commands are copy/paste ready.
  • Security-sensitive steps call out secret handling and least privilege.
  • Version-sensitive guidance cites current docs used.
  • Rollback path is included for risky changes.
  • Final output includes quick validation commands/tests.
#mcp#testing#contracts#reliability#api

Source citations

Add this badge to your README

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Listed on HeyClaude
[![Listed on HeyClaude](https://heyclau.de/badge/skills/mcp-tool-contract-testing.svg)](https://heyclau.de/entry/skills/mcp-tool-contract-testing)

How it compares

MCP Tool Contract Testing Skill side by side with 2 alternatives on trust, install, platform support, and disclosed safety notes — all from reviewed registry metadata.

1 trust signal differ across this comparison (Source provenance).

Field
MCP Tool Contract Testing Skill

Validate MCP server tools with contract-style tests to catch schema drift, unsafe behavior, and integration regressions early.

Open dossier
MCP Server Authoring Security Capability Pack Skill

Expert MCP capability skill for secure server authoring, tool schema discipline, authorization boundaries, and prompt-injection risk review.

Open dossier
MCP Server Security Hardening Skill

Secure MCP servers with strict tool boundaries, auth controls, dependency hygiene, and abuse-resistant runtime policies.

Open dossier
Next steps
Open dossierAPI JSONOpen LLMOpen sourceNewsletterClaim listing
Open dossierAPI JSONOpen LLMOpen sourceNewsletterClaim listing
Open dossierAPI JSONOpen LLMOpen sourceNewsletterClaim listing
Trust
Review statusReviewedMaintainer reviewedReviewedMaintainer reviewedReviewedMaintainer reviewed
Package trustPackage verified2026-04-10Package verified2026-04-10Package verified2026-04-10
Source provenanceDiffersSource-backedNo submission linkNo submission link
Submitter———
Install riskReview firstLow riskLow risk
Notes Safety ✓ Privacy ✓ Safety ✓ Privacy ✓ Safety ✓ Privacy ✓
Brand———
Categoryskillsskillsskills
Sourcefirst-partyfirst-partyfirst-party
AuthorJSONboredJSONboredJSONbored
Added2026-04-102026-04-102026-04-10
Platforms
Claude CodeCodexWindsurfGeminiCursorCLI
Claude CodeCodexWindsurfGeminiCursorCLI
Claude CodeCodexWindsurfGeminiCursorCLI
Source repo———
Safety notes✓Use this skill as planning or review guidance; verify generated commands, code, configuration, and infrastructure changes before running them. Apply least-privilege credentials and test in staging or a disposable branch before using it on production systems, CI, deployment, or account-write workflows.✓Use the skill as a review and implementation checklist; do not deploy MCP auth, credential flow, or permission changes without human review. Validate tool schemas, authorization decisions, and logging behavior with tests before exposing an MCP server to real users or external clients. Treat generated threat models as incomplete until checked against current MCP security and authorization docs.✓Treat findings and generated mitigations as review inputs; validate suspected vulnerabilities and patches before changing production controls. Coordinate disclosure-sensitive security work privately and avoid running destructive probes outside authorized systems.
Privacy notes✓Inputs can include source files, prompts, logs, account metadata, repository details, and operational context that may be sent to the configured AI model. Redact secrets, customer data, private URLs, credentials, and proprietary implementation details before sharing prompts, reports, or generated artifacts.✓Tool inventories, auth flows, logs, incident examples, prompts, and server code shared with this skill may enter model context. Redact access credentials, client secrets, user records, tenant identifiers, and production request bodies before using them as examples.✓Security prompts and reports can include source snippets, vulnerability details, internal URLs, dependency metadata, and operational context. Redact secrets, customer data, exploit details, private infrastructure names, and unreleased findings before sharing outputs publicly.
Prerequisites
  • MCP server implementation and tool catalog
  • Staging environment for test execution
  • Known expected outputs per critical tool
  • MCP server implementation or design draft
  • Tool inventory and expected consumers
  • Logging/alerting sink for security events
  • Existing MCP server implementation (local or remote)
  • Access to server config, dependency manifest, and deployment settings
  • Ability to run integration tests after hardening
Install
curl -L https://heyclau.de/downloads/skills/mcp-tool-contract-testing.zip -o mcp-tool-contract-testing.zip && unzip -o mcp-tool-contract-testing.zip -d ./mcp-tool-contract-testing
curl -L https://heyclau.de/downloads/skills/mcp-server-authoring-security-capability-pack.zip -o mcp-server-authoring-security-capability-pack.zip && unzip -o mcp-server-authoring-security-capability-pack.zip -d ./mcp-server-authoring-security-capability-pack
curl -L https://heyclau.de/downloads/skills/mcp-server-security-hardening.zip -o mcp-server-security-hardening.zip && unzip -o mcp-server-security-hardening.zip -d ./mcp-server-security-hardening
Config———
Citations
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