Telemetry: emit per-tool identifier via CosmosClient ApplicationName so DailyUserAgentSummary can break down by tool

[sajeetharan]

Telemetry: emit per-tool identifier via CosmosClient ApplicationName

Problem

DailyUserAgentSummary.UserAgent is the only field our downstream dashboards can bucket by, and today it cannot break down MCP Toolkit calls by tool. Every one of the 8 [McpServerTool] methods in [McpServerToolType] CosmosDbTools (in src/AzureCosmosDB.MCP.Toolkit/Program.cs) constructs its CosmosClient with the same hardcoded value:

using var client = new CosmosClient(endpoint, credential, new CosmosClientOptions
{
    ApplicationName = "AzureCosmosDBMCP"
});

The tool name currently only lives in ILogger messages (e.g. "Listing databases from Cosmos DB", "Received MCP tool call: {ToolName}"). Those logs flow to stdout / Container Apps / App Insights — not into the Cosmos SDK UserAgent that surfaces in DailyUserAgentSummary.UserAgent. So the per-tool signal simply isn't in the telemetry the dashboard reads.

Fix

Encode the tool name into ApplicationName using the format:

AzureCosmosDBMCP-<kebab-tool-name>

Separator - (dash) avoids collision with / and , which the Cosmos SDK already uses in its own UA segments, giving an unambiguous regex.

Mapping

Method	ApplicationName
ListDatabases	AzureCosmosDBMCP-list-databases
ListCollections	AzureCosmosDBMCP-list-collections
GetRecentDocuments	AzureCosmosDBMCP-get-recent-documents
TextSearch	AzureCosmosDBMCP-text-search
FindDocumentByID	AzureCosmosDBMCP-find-document-by-id
GetApproximateSchema	AzureCosmosDBMCP-get-approximate-schema
VectorSearch	AzureCosmosDBMCP-vector-search
HybridSearch	AzureCosmosDBMCP-hybrid-search

KQL (dashboard tile)

DailyUserAgentSummary
| where UserAgent has "AzureCosmosDBMCP-"
| extend Tool = extract(@"AzureCosmosDBMCP-([a-z][a-z0-9-]*)", 1, UserAgent)
| where isnotempty(Tool)
| summarize Requests = sum(Count) by Tool, bin(Date, 1d)
| render columnchart

Scope

• Change 8 ApplicationName string literals in src/AzureCosmosDB.MCP.Toolkit/Program.cs.
• Add a short comment near the first modified site documenting the convention for future [McpServerTool] additions.
• Not changing the singleton CosmosClient built in CosmosClientFactory.BuildClientOptions — it feeds CosmosDbToolsService, which is not on the MCP tool path today, and a singleton fundamentally cannot carry a per-tool suffix. Documented as a known limitation.

Spec

Full spec: docs/specs/tool-name-in-useragent.md

Acceptance criteria

• Each of the 8 [McpServerTool] methods emits a distinct ApplicationName matching the table above.
• Build passes (dotnet build).
• Comment near the first modified site documents the convention.
• Spec file docs/specs/tool-name-in-useragent.md merged alongside code change.
• Dashboard tile using the KQL above successfully bins requests by tool after next deployment.