How do I install the API Diff skill?

Run npx skillmds@latest add dotnet/api-diff in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is API Diff free to use?

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Who published API Diff?

.NET (Microsoft) (@dotnet) published this skill. Their other Agent Skills are listed on their SkillMD profile.

API Diff by dotnet — Agent Skill

Name: API Diff
Rating: 4.5 (4 reviews)
Author: .NET (Microsoft)

API Diff

Generate before/after .NET public API diff reports for a release milestone with `RunApiDiff.ps1`. Pure report generation only; to verify the diff against the shipped build (dotnet-inspect, revert detection) use the api-diff-validation skill.

.NET (Microsoft) Updated Sep 10, 2026 4k repo stars

File contents

API Diffing

Use this skill to produce the markdown-ready, repo-shaped API diff reports for a release milestone (previous milestone -> current). This skill is pure generation: it runs the diff tool and writes the reports. Verifying that the diffed APIs actually shipped, tracing them to PRs, and catching reverts is the separate api-diff-validation skill.

Generate the reports with `RunApiDiff.ps1`

Use release-notes/RunApiDiff.ps1. See release-notes/RunApiDiff.md for the full parameter reference.

Mapping natural language to parameters

User says	Parameters
"generate the next API diff"	(none)
".NET 10 GA vs .NET 11 Preview 1"	`-PreviousMajorMinor 10.0 -CurrentMajorMinor 11.0 -CurrentPrereleaseLabel preview.1`
"net9.0-preview6 to net10.0-preview5"	`-PreviousMajorMinor 9.0 -PreviousPrereleaseLabel preview.6 -CurrentMajorMinor 10.0 -CurrentPrereleaseLabel preview.5`
".NET 10 RC 2 vs .NET 10 GA"	`-PreviousMajorMinor 10.0 -PreviousPrereleaseLabel rc.2 -CurrentMajorMinor 10.0`
"10.0.0-preview.7.25380.108 to 10.0.0-rc.1.25451.107"	`-PreviousVersion "10.0.0-preview.7.25380.108" -CurrentVersion "10.0.0-rc.1.25451.107"`

GA or no qualifier -> omit the PrereleaseLabel parameter for RunApiDiff.ps1; if a downstream api-diff release label is needed, use ga
Preview N / previewN -> -PrereleaseLabel preview.N (for example, preview.4, not preview4)
RC N / rcN -> -PrereleaseLabel rc.N
Alpha N / Beta N -> -PrereleaseLabel <label>.N (for example, alpha.1, beta.2); RunApiDiff.ps1 accepts only the alpha, beta, preview, and rc prerelease labels
netX.Y-previewN (TFM format) -> -MajorMinor X.Y -PrereleaseLabel preview.N
Full NuGet version strings -> use -PreviousVersion / -CurrentVersion directly
The "previous" version is always the older version; "current" is the newer one

Running the script

.\release-notes\RunApiDiff.ps1 [mapped parameters]

Set an initial wait of at least 300 seconds — the script takes several minutes. After completion, summarize the results: how many diff files were generated and where.

---name: api-diffdescription: Generate before/after .NET public API diff reports for a release milestone with `RunApiDiff.ps1`. Pure report generation only; to verify the diff against the shipped build (dotnet-inspect, revert detection) use the api-diff-validation skill.---# API DiffingUse this skill to produce the markdown-ready, repo-shaped **API diff reports** for arelease milestone (previous milestone -> current). This skill is pure generation: itruns the diff tool and writes the reports. Verifying that the diffed APIs actuallyshipped, tracing them to PRs, and catching reverts is the separate[api-diff-validation](../api-diff-validation/SKILL.md) skill.## Generate the reports with `RunApiDiff.ps1`Use `release-notes/RunApiDiff.ps1`. See [release-notes/RunApiDiff.md](../../../release-notes/RunApiDiff.md) for the full parameter reference.## Mapping natural language to parameters| User says | Parameters || ----------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------- || "generate the next API diff" | _(none)_ || ".NET 10 GA vs .NET 11 Preview 1" | `-PreviousMajorMinor 10.0 -CurrentMajorMinor 11.0 -CurrentPrereleaseLabel preview.1` || "net9.0-preview6 to net10.0-preview5" | `-PreviousMajorMinor 9.0 -PreviousPrereleaseLabel preview.6 -CurrentMajorMinor 10.0 -CurrentPrereleaseLabel preview.5` || ".NET 10 RC 2 vs .NET 10 GA" | `-PreviousMajorMinor 10.0 -PreviousPrereleaseLabel rc.2 -CurrentMajorMinor 10.0` || "10.0.0-preview.7.25380.108 to 10.0.0-rc.1.25451.107" | `-PreviousVersion "10.0.0-preview.7.25380.108" -CurrentVersion "10.0.0-rc.1.25451.107"` |- **GA** or no qualifier -> omit the `PrereleaseLabel` parameter for `RunApiDiff.ps1`; if a downstream api-diff release label is needed, use `ga`- **Preview N** / **previewN** -> `-PrereleaseLabel preview.N` (for example, `preview.4`, not `preview4`)- **RC N** / **rcN** -> `-PrereleaseLabel rc.N`- **Alpha N** / **Beta N** -> `-PrereleaseLabel <label>.N` (for example, `alpha.1`, `beta.2`); `RunApiDiff.ps1` accepts only the `alpha`, `beta`, `preview`, and `rc` prerelease labels- **netX.Y-previewN** (TFM format) -> `-MajorMinor X.Y -PrereleaseLabel preview.N`- Full NuGet version strings -> use `-PreviousVersion` / `-CurrentVersion` directly- The "previous" version is always the older version; "current" is the newer one## Running the script```powershell.\release-notes\RunApiDiff.ps1 [mapped parameters]```Set an initial wait of at least 300 seconds — the script takes several minutes. After completion, summarize the results: how many diff files were generated and where.

Frequently asked questions