Linter: avoid `Microsoft`/`Azure` prefix on model / class names

[haiyuazhang]

Parent: #4442

Convention

Avoid using Microsoft, Azure prefixes for any models or classes.

Source: Azure SDK for .NET Mgmt Naming Conventions

Observed today

A scan of Azure/azure-rest-api-specs (334 client.tsp files, 10,754 csharp-scoped @@clientName decorators) shows 164 decorators currently encoding this rule by hand. Examples:

• AzureFunctionDefinition → InternalAzureFunctionDefinition (ai/Azure.AI.Agents/client.tsp)
• AzureBlobContentSource → BlobContentSource (ai/DocumentIntelligence/client.tsp)
• AzureBlobFileListContentSource → BlobFileListContentSource (ai/DocumentIntelligence/client.tsp)
• AzureApiManagementSource → ApiCenterApiManagementSource (apicenter/ApiCenter.Management/client.tsp)
• AzureMonitorExporter → ApplicationInsightsRestClient (applicationinsights/data-plane/Exporters/client.tsp)
• AzureLargeStorageInstance → LargeStorageInstance (azurelargeinstance/resource-manager/Microsoft.AzureLargeInstance/AzureLargeInstance/client.tsp)

Proposed linter

Detection

Flag any model whose name starts with Microsoft or Azure (case-sensitive). Allow well-known service identity types via a known-prefixed-types allowlist.

Auto-fix

Suggest dropping the prefix via @@clientName(..., "csharp").

Scope

The rule should be csharp-scoped — it only flags violations of the .NET convention, not the underlying TypeSpec name. It should suggest inserting a @@clientName(..., "csharp") override when the underlying TypeSpec name is intentional, or renaming the TypeSpec model when the convention applies cross-language.

Acceptance criteria

• New lint rule registered in the appropriate ruleset (@azure-tools/typespec-client-generator-core or @azure-tools/typespec-azure-resource-manager).
• Doc page under website/src/content/docs/docs/libraries/.../rules/.
• Unit tests covering positive / negative cases and the auto-fix.
• A .chronus/changes/ entry.

[markcowl]

I don't think this should be a linter rule, because this is more of a suggestion than a hard and fast rule. I would suggest that this becomes instructions for agent skills (authoring and review) rather than a hard and fast linting rule.

[haiyuazhang]

Impact analysis: Microsoft/Azure prefix models

Findings

• 625 Microsoft*/Azure* models total
• In specs with client.tsp: 577 (renamed: 45, would trigger: 532)
• Only 8% adoption rate
• Many models use Azure as part of a legitimate product name (e.g., AzureActiveDirectory, AzureADAdministrator, AzureDataExplorer) — not a naming convention violation

Recommendation: Not a good candidate for implementation now

532 violations is very high. Many Azure* models are legitimate product names where the prefix is part of the identity (e.g., AzureActiveDirectory, AzureDevOps). A rule would need an allowlist of legitimate Azure-prefixed product names, which is hard to maintain and prone to false positives.