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Share one implementation between CLI commands and MCP tools

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Refactor
Clarity
Mostly clear
Activity status
Active
Tech stack
csharp
Domain
backend-api-design, cli, tooling

Research direction

Read AGENTS.md and the registrations in Features/Mcp/McpHostCommand.cs, then inspect LeaveUpdateService and the Timesheet update CLI and MCP adapters for migration slice 1. Done means the adapters use one shared service, the architecture and parity tests enforce delegation, and established --json wire shapes remain unchanged.

Written by the indexing model from the issue text.

Description

Priority: P1 Type: Refactor

Why

47 MCP tools (18 default, 29 accounting-gated) are registered in Features/Mcp/McpHostCommand.cs. Only four share a service with their CLI counterpart (LeaveCreateService, LeaveUpdateService, LeaveBalanceImportService, WeekCoverageService). The other 43 re-implement the orchestration the CLI command already does, so every fix lands twice or, as with #21, only once. AGENTS.md already states the rule ("MCP delegates to the same service"); this issue makes the codebase follow it and adds a test that keeps it that way.

Inventory (where sharing is missing)

MCP tool CLI command Today
GetTimesheets ts get duplicate; MCP skips weekends, CLI does not
CreateTimesheet ts create duplicate; CLI also resolves rate, category, deducted time
UpdateTimesheet ts update duplicate, destructive (#21)
DeleteTimesheet / AcceptSuggestedTimesheet ts delete / ts accept duplicate; empty-response handling differs
GetSuggestedTimesheets ts suggest duplicate; note this refreshes server state, it is not read-only
CheckWeek ts check shared service, duplicated projection
SearchClients / GetProjectsForClient / GetClientRate / GetCrmBookings / ListIterations client search / project list / rate get / booking list / iteration list duplicate; missing-rate result differs
GetLeaveEntries / GetLeaveBalance / GetLeaveBalanceStatus leave list / leave balance / leave balances status duplicate
All accounting tools (invoices, receipts, credit notes, products, rates, unbilled, recurring, query, summary, prepaid) matching tp commands duplicate; prepaid calculation lives in TimeProApiClient
GetInvoicesByClient, GetUnpaidInvoicesByClient, ListCategories, ListBillableTypes, ListAllSkus none MCP-only, violates the "CLI first" rule
none leave cancel CLI-only

Target architecture

  • Per feature: Services/ with a request record, result record and a service that owns validation, defaults, lookups, read-merge and API orchestration. No single giant service.
  • CLI command = parse settings, build request, call service, render table or JSON, choose exit code.
  • MCP tool = bind args, build the same request, call the same service, serialize the same result record. Never shell out to tp.
  • One result type feeds both --json and MCP structured content. One serializer policy (OutputHelper omits nulls and stringifies enums; MCP classes currently differ).
  • One application error type (category, nullable API status, safe message, recovery hint, mayHaveBeenApplied). CLI maps it to the {"error":{...}} envelope plus exit code; MCP maps it to CallToolResult.IsError = true. Today MCP returns {"error":"..."} strings that look like successful results.
  • Writes with previews follow the LeaveUpdateService shape: PrepareAsync (no writes) then ApplyAsync. CLI --dry-run and MCP dryRun call the same preparation.
  • Adapter-only: prompts, --yes, table formatting, file vs base64 output, exit codes. MCP confirmations use client approval or elicitation; a model-supplied confirmed=true is not consent.

Enforcement

  • Architecture test: no ITimeProApiClient, HttpClient, or console access from Features/Mcp/Tools. Reflection can check dependencies; use Roslyn or IL inspection if delegation itself must be proven.
  • Every [McpServerTool] maps to a shared service and a registered CLI command, with a temporary allowlist for unmigrated tools that may only shrink.
  • Adapter parity tests against the same fake service; snapshot tools/list names, schemas and annotations.

Migration order

# Slice Size
1 TimesheetUpdateService, both update adapters (fixes #21; also home for #22 --iteration) M
2 Timesheet create (shared rate/category/location logic; no implicit MCP writes) L
3 Delete, accept, and normalising leave/import outcomes M
4 Timesheet reads, suggestions, week coverage (explicit weekend policy) M
5 Prepaid and accounting reads (move prepaid maths out of TimeProApiClient) M each
6 Lookups and the MCP-only / CLI-only gaps above S each
7 Remove allowlist and legacy projections S

Do not change established --json wire shapes while extracting; schema changes are separate, explicit PRs. Do this before the SDK upgrade (#39).

Dominant language
C#
Stars
3
Forks
0
Avg merge
7m
Merged PRs (30d)
30

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