feat(mcp): add a read-only MCP server for certification state - #288
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Operators increasingly run agents alongside NVCRE. Answering 'did this certification pass, and which nodes failed?' today means a person running the CLI and reading CRD status — a repetitive lookup loop an agent could run, but only against a typed interface rather than scraped CLI output. Add 'nvcrectl mcp serve' on the official Go MCP SDK (github.com/modelcontextprotocol/go-sdk v1.7.0, served over stdio). It exposes four read-only tools backed by the same data sources nvcrectl uses: list_categories (pkg/catalog), get_certification_status (Certification status + pkg/report.CertFailedNodes), get_certification_report (pkg/report.Build — the same JSON that 'report --results-file' writes), and list_failed_nodes (per-node reason/message from the failed-nodes ConfigMaps via pkg/report.FailedNodesFromRef). The server is deliberately read-only (issue NVIDIA#242): no tool creates, mutates, or deletes a resource and nothing triggers a run, since runs consume real GPU time. All tools carry the MCP readOnlyHint annotation. Authentication flows strictly through the caller's kubeconfig via the standard client-go loading rules (--kubeconfig/--context flags, then KUBECONFIG, then ~/.kube/config), so an agent can never exceed the permissions of whoever launched it; no service account tokens, no credential storage. Tests drive a full MCP session over in-memory transports against a fake client: a golden-file test pinning all four tools' JSON output, plus checks that exactly four read-only-annotated tools are exposed and that not-found certifications return a tool error. Signed-off-by: The Anh Nguyen <ntheanh201@gmail.com>
THIRD_PARTY_NOTICES.md lists the license of every direct dependency of the nvcrectl binary and ships as a release asset, so the new MCP SDK dependency belongs here. There is no generator target for this file; it is maintained by hand (as in dbf9121), so this adds the v1.7.0 index entry and the verbatim license text. The SDK is in a MIT-to-Apache-2.0 licensing transition, hence both licenses listed. Signed-off-by: The Anh Nguyen <ntheanh201@gmail.com>
get_certification_status walked the Certification CR and re-derived the
verdict itself, so it drifted from the report every other surface prints:
- it never applied the PASSED -> INCOMPLETE downgrade report.Build makes
when a Workflow excluded nodes (report.go:308), and carried no
excludedNodes field at all. A run that left eight of forty nodes
untested was reported to an agent as PASSED, in the cheaper tool an
agent reaches for first.
- it returned the raw InProgress category status where the report says
Running, so the two tools disagreed on vocabulary for the same object.
Project the summary from report.Build instead. The agreement stops being a
convention two code paths must maintain and becomes structural, and
excludedNodes/exclusionReason are surfaced so the INCOMPLETE verdict is
explainable rather than bare.
TestStatusAgreesWithReport asserts the two tools describe a Certification
identically across every fixture. The golden files could not have caught
this class: they record each tool independently, so a divergence sits
unnoticed in two blocks sixty lines apart. A new excluded-nodes fixture
covers the INCOMPLETE path; reintroducing the bug fails both the new
assertion and that golden.
Also corrects the tool descriptions, which are the model's contract:
get_certification_report no longer advertises per-node results, which
report.Build never populates, and list_failed_nodes now says it returns one
row per distinct reason and points at get_certification_status.failedNodes
for a unique node count.
Signed-off-by: The Anh Nguyen <ntheanh201@gmail.com>
AGENTS.md requires an ADR for a new component; the MCP server landed without one. ADR-075 records the decisions that are not obvious from the code: why the surface is read-only (a run occupies the fleet it certifies, so the write surface is what needs justifying), why every verdict is projected from report.Build rather than re-derived, and why the two failed-node views deliberately differ. It also corrects a security claim that was not true. The docs, the cobra help and the package doc each stated the server "never reads in-cluster service account tokens". pkg/kubeconfig uses client-go's standard loading rules, which end in an in-cluster fallback: run `nvcrectl mcp serve` in a pod with no kubeconfig and it authenticates as that pod's ServiceAccount, which may be broader than the operator running the agent. The tools stay read-only either way, so this is a confidentiality claim rather than a privilege-escalation bug — but a guarantee that only holds outside a pod is worse than none, in a feature aimed at agents that commonly run in-cluster. State the resolution order accurately instead, and document the RBAC the tools need. That includes the ConfigMap read: pkg/report returns empty results rather than errors when it cannot read node results, so a caller missing that permission is told "no nodes failed" when the truth is "not allowed to look". Signed-off-by: The Anh Nguyen <ntheanh201@gmail.com>
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Included review availability: Your plan provides up to 12 included reviews per hour; 11 remain after this review. 📝 WalkthroughWalkthroughThe change adds a read-only MCP server for NVCRE certification state. The Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to The new MCP server is read-only and uses the caller’s Kubernetes identity, but its documented permissions do not cover every resource needed to build certification reports; insufficient access can cause failures or misleadingly incomplete failed-node results. The PR is mergeable with explicit owner awareness to align RBAC and authorization-error handling. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Out of Scope Changes checkExplanation The changes remain within the requested MCP feature, including CLI integration, documentation, design records, dependency notices, tests, and read-only behavior. No unrelated code changes are identified. Full details: Docstring CoverageExplanation Docstring coverage is 69.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 23 functions across 5 files. (1 skipped: 1 unsupported.)
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Inline comments:
In `@docs/cli-reference/mcp.md`:
- Line 24: Update the get_certification_status result documentation to include
INCOMPLETE alongside PASSED, FAILED, and RUNNING, reflecting the value returned
when excluded nodes downgrade a passed certification.
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THIRD_PARTY_NOTICES.mdis excluded by!THIRD_PARTY_NOTICES.mdgo.sumis excluded by!**/*.sumpkg/mcpserver/testdata/mcp-tools/basic/expected.txtis excluded by!**/testdata/**pkg/mcpserver/testdata/mcp-tools/basic/input_calls.jsonis excluded by!**/testdata/**pkg/mcpserver/testdata/mcp-tools/basic/input_client_objects.yamlis excluded by!**/testdata/**pkg/mcpserver/testdata/mcp-tools/excluded-nodes/expected.txtis excluded by!**/testdata/**pkg/mcpserver/testdata/mcp-tools/excluded-nodes/input_calls.jsonis excluded by!**/testdata/**pkg/mcpserver/testdata/mcp-tools/excluded-nodes/input_client_objects.yamlis excluded by!**/testdata/**
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cmd/nvcrectl/main.godocs/cli-reference/mcp.mddocs/cli-reference/overview.mddocs/designs/075-mcp-server.mddocs/designs/README.mddocs/index.ymlgo.modpkg/mcp/command.gopkg/mcpserver/codec.gopkg/mcpserver/server.gopkg/mcpserver/server_test.go
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The tool table listed the status result as PASSED/FAILED/RUNNING. The tool returns INCOMPLETE too, and it is the value that matters most to a reader: it means the run passed but left targeted nodes untested, so treating it as a pass is exactly the mistake the value exists to prevent. Document what it means, not just that it exists. The report row promised per-node results in the same table. report.Build never populates NodeResults -- only pkg/workloadrun does -- so the promise was empty. The tool description in server.go was already corrected; this brings the docs in line. Also states the deliberate difference between the two failed-node views, since a caller counting rows from list_failed_nodes will over-count a node that failed in several categories. Signed-off-by: The Anh Nguyen <ntheanh201@gmail.com>
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Summary
Adds
nvcrectl mcp serve: a read-only MCP server over stdio exposing four tools —list_categories,get_certification_status,get_certification_report,list_failed_nodes— so an agent can answer "did this certification pass, and which nodes failed?" against a typed interface instead of scraped CLI output.The load-bearing decision is that every certification verdict is projected from
report.Buildrather than re-derived from the CR. An earlier draft of this change walked the Certification itself, and drifted from the report in three ways before anything noticed:PASSED→INCOMPLETEdowngradereport.Buildmakes when a Workflow excluded nodes (report.go:308), and carried noexcludedNodesfield — so a run that left 8 of 40 nodes untested was reported to an agent asPASSED, in the cheaper tool an agent reaches for first;InProgresscategory status where the report saysRunning;report.CertFailedNodes.Projecting from the report makes agreement structural rather than a convention two code paths have to maintain.
TestStatusAgreesWithReportpins it across every fixture — the golden files could not, since they record each tool independently and a divergence sits unnoticed in two blocks 60 lines apart.Stdio only: the agent spawns the process, which avoids introducing a network listener and the bearer-token/OAuth design that would come with it. No tool creates, mutates, or deletes anything, and none triggers a run —
TestListToolsfails if a fifth or mutating tool is ever added. ADR-075 records the reasoning.Related Issue
Closes #242
Type of Change
Component(s) Affected
New dependency — needs a maintainer call
This adds
github.com/modelcontextprotocol/go-sdk v1.7.0, the first MCP dependency ingo.mod. It lands in thenvcrectlbinary, not the controller.THIRD_PARTY_NOTICES.md).google/jsonschema-go,golang-jwt/jwt/v5,segmentio/asm,segmentio/encoding,yosida95/uritemplate/v3.THIRD_PARTY_NOTICES.mdappears to be hand-maintained (no generator target found), so I edited it by hand. If you have ago-licenses-style generator, my entry will want reformatting.Happy to drop the SDK and hand-roll the JSON-RPC framing instead if a new dependency is unwelcome here.
Also in this PR
Two corrections that came out of reviewing the above:
pkg/kubeconfiguses client-go's standard loading rules, which end in an in-cluster fallback — runmcp servein a pod with no kubeconfig and it authenticates as that pod's ServiceAccount. The tools stay read-only, so this is a confidentiality claim rather than privilege escalation, but a guarantee that only holds outside a pod is worse than none in a feature aimed at agents. Now stated accurately, with the RBAC the tools need.pkg/reportreturns empty results rather than errors when it cannot read a Workflow or the node-results ConfigMap, so a caller lacking that permission is told"failedNodes": []when the truth is "not allowed to look". Fine for a CLI a human reads; worth knowing for a tool an agent quotes. I did not change that shared behaviour in this PR.Testing
make cipasses on the branch: 25 packages,golangci-lint0 issues, including the envtest integration suite.Unit and golden coverage:
TestMCPToolsdrives a real MCP session over in-memory transports (initialize → tools/list → tools/call) rather than mocking;TestNotFoundasserts a tool error with the nvcrectl-style message;TestListToolspins the four-tool read-only surface;TestStatusAgreesWithReportasserts the two tools describe a Certification identically. A newexcluded-nodesfixture covers theINCOMPLETEpath — reintroducing the bug fails both that assertion and the golden.Validated against a live cluster (Kubernetes v1.35.3, 2 nodes, GPU Operator present), not just envtest:
Certification/Workflowobjects:excludedNodesINCOMPLETEfrom both tools,excludedNodessurfacedInProgressRunningin both toolsHardwareFailureDetected,ThresholdViolation)status.result==report.resultThe cluster was returned to its prior state afterwards (
setup resetplus manual removal of the namespaces and CRDs).Risk
Low, and additive. New package plus one new
nvcrectlcommand group; no controller, CRD, or reconciler changes; nothing in the install path. The surface is read-only by construction and pinned by a test. The real risk is the new dependency, called out above.Two things deliberately out of scope: no HTTP/SSE transport (it needs its own auth design), and no ability to trigger runs — runs consume real GPU time and that deserves its own decision about consumption and preemption.
Checklist
git commit -s)make manifests generaterun (if*_types.gowas modified) — n/a, no API types changed