mcp-calltoolfilter-tests

name	mcp-calltoolfilter-tests
description	Test MCP CallToolFilter behavior with real CallToolRequestParams and McpServerTool invocation.
domain	mcp-testing
confidence	high
source	earned

Context

Use this when validating McpServerOptions.Filters.Request.CallToolFilters, especially filters that mutate inbound CallToolRequestParams.Arguments before SDK parameter binding.

Pattern

• Unit-test the filter by wrapping a capture handler and asserting the request's argument dictionary after the filter runs.
• For binding behavior, wrap McpServerTool.InvokeAsync created from the real attributed tool method; this exercises SDK binding instead of a helper-only path.
• Construct RequestContext<CallToolRequestParams> with a real CallToolRequestParams { Name = toolName, Arguments = ... } and JSON-backed JsonElement values via JsonSerializer.SerializeToElement.
• Assert both success routing and failure wrapping: missing required arguments should still become the repo's structured McpException.

Example Scenarios

• Alias-only argument normalizes before binding.
• Canonical parameter wins when canonical and alias are both present.
• Multiple aliases have documented precedence.
• Non-standard alias casing is accepted when the alias table is case-insensitive.
• Test with realistic value types from telemetry, not just sanitized strings; numeric JsonElement aliases should be covered when callers send IDs as JSON numbers.