Microsoft Project README
The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Microsoft Project listing page.
Horizun Project MCP
An MCP server for Microsoft Project that needs neither Java nor Microsoft Project — and tells you the truth about what it wrote.
Point any MCP client at a .mpp, a Primavera .xer, or an MSPDI .xml and ask real questions:
where the critical path runs, which resources are overbooked, whether the schedule would survive a
DCMA audit, what a two-week slip actually does to the finish date. Then write changes back — and
know which ones landed, because every one is re-read from the model before it is reported.
That is the whole install. No JVM. No Microsoft Project. No licence. It reads and schedules on its own.
Connect a client
| Client | Do this |
|---|---|
| Claude Desktop | Download the .mcpb from Releases and drop it on Settings → Extensions. It installs the server itself — nothing to run first. |
| Claude Code | claude mcp add horizun-msproject-mcp -- horizun-msproject-mcp |
| Codex | codex mcp add horizun-msproject-mcp -- horizun-msproject-mcp |
| ChatGPT | Needs an HTTPS bridge in front of the stdio server. How, and what to weigh first. |
Full per-client instructions, including the plugin route and uninstall, are in docs/INSTALL.md.
Why this one
There are a handful of Microsoft Project MCP servers. Every one of them requires Java, or a licensed Microsoft Project install, or a paid JDBC driver — and on the machine this was built on, none of them would start. Eight things here are not available anywhere else:
| Zero prerequisites | A single .NET binary. MPXJ is compiled to .NET through IKVM, so there is no JVM anywhere in the picture, and no Microsoft Project either. |
| Microsoft Project's dates, not an imitation | Where Project is installed, Project itself calculates every date this server reports. On seven real schedules — 8,823 tasks — recalculations and edits made through it matched Project on every task, to the minute. How. |
| Verified writes | Microsoft Project silently ignores writes all the time — auto-scheduled dates, hard constraints, summary rollups, calculated costs. Nothing here is reported as applied until it has been read back out of the model and matched. |
| DCMA 14-point assessment | The industry standard for judging whether a schedule can be run on. The Primavera servers implement it; none of the Microsoft Project ones do. Check 12 genuinely injects a 600-day delay and measures what moves. |
| It recovers logic nobody linked | A schedule laid out correctly on the bar chart but never linked is the most common defect there is: DCMA flags it, nothing fixes it. The dates already state the order — this reads it back out, verifies the same order holds across every repetition, and proposes the missing links. |
| Reprogramming that is measured | Recovery options are applied to a copy of the schedule, rescheduled, and reported with the finish date they actually produce. An option that recovers nothing says so instead of being offered as advice. |
| It learns from your past projects | Point it at finished schedules and it reports what each activity really took and what usually precedes it, then drafts a new programme from that — one task per unit, sequenced the way the trades actually followed each other. |
| A BIM bridge | Tie schedule tasks to model elements by code, turn measured quantities into duration proposals, and emit the per-element dates that drive 4D in Navisworks and the progress dashboard in Power BI. Nobody else does this at all. |
The 25 tools
Session — project_health · project_open · project_save
project_health is a doctor, not a ping. It detects Microsoft Project, tests whether its COM server
actually starts, and when it does not, hands back the HRESULT diagnosis and the repair steps. That
is not hypothetical: this machine hit CO_E_SERVER_EXEC_FAILURE with a perfectly valid registration,
and step one of the repair path it emits is what fixed it.
Reading — project_info · tasks_query · links_query · resources_query · timephased_query
Filtered, paged, field-selectable. Tasks are addressed by their stable uid; the row id is display
only, because it shifts the moment a task is inserted and addressing by it edits the wrong task.
Analysis — schedule_analyze · schedule_qa · baseline_compare
Computed server-side, so the agent asks a question instead of pulling two thousand tasks into context. Critical path, float distribution, driving path, day-by-day overallocation, DCMA-14, and full earned value (BCWS/BCWP/ACWP, SPI, CPI, EAC, TCPI) — denominated in cost where the schedule carries costs, in work hours where it carries hours, and weighted by duration where it carries neither, which is most of them. The report says which.
Writing — tasks_write · links_write · resources_write · calendars_write · schedule_update
Batched, typed, verified. Cycles are refused before they are applied, with the offending chain named. Two things this backend cannot do are not offered: reordering a task within the outline, and editing a calendar's weekly working-hours pattern. Asking for either gets a refusal that names it and says where to do it instead — an operation that half-works is worse than one that is absent.
Planning — schedule_recovery · schedule_target · schedule_sequence · schedule_learn · schedule_generate
Reprogramming, measured rather than asserted. schedule_recovery finds what is late, ranks it by
how much of the schedule sits behind it, then tries each recovery lever — removing lag on the
driving chain, overlapping hand-offs, compressing the longest critical tasks — on a throwaway copy
and reports the finish date each one genuinely produces. schedule_target tests a date you have
been handed and names the work the network does not hold in place. schedule_sequence recovers the
logic a schedule is missing by reading the order its own dates already state — the planner laid the
work out correctly and never linked it, and that decision is recoverable. schedule_learn mines finished
schedules for how long each activity actually takes and what usually comes before it;
schedule_generate turns that into a first draft, one task per apartment or floor, sequenced the
way the history says the trades follow each other.
Feed schedule_learn a model export alongside the schedules and it measures productivity —
what a crew actually got through in a day — by joining quantities to tasks on the shared code.
schedule_generate then sizes durations from the quantities of the new project rather than
copying a remembered duration, because the rate is what carries between projects and the quantity
is what changes. Give one export per schedule, in the same order: rates are measured per project,
and quantities totalled across projects would inflate every one of them.
A draft can only be as well sequenced as the schedules it learned from. Where the sources link each activity to itself unit after unit but never to the trades around it, both tools say so and name the number: the library reports how many activities learned a predecessor other than themselves, and the draft reports how many trades it left with nothing scheduled before them.
Interop — project_export · project_import · bim_link · bim_sync
CSV, JSON, MSPDI, Primavera XER and PMXML, native .mpp, and a shaped Power BI dataset. Imports
plan before they write.
What it costs to have loaded
The 25 tools present about 8,400 tokens of schema, in every prompt, for as long as the server is connected. That is the honest price of the surface and it is worth knowing before choosing to carry it. It is also why the surface stayed at 25: the largest alternative ships 79 tools, and past a point an agent cannot hold the surface in its head well enough to choose correctly within it.
The two contracts
Nothing is applied until it is verified.
A dry run is a real simulation. dryRun: true deep-copies the schedule, applies the batch,
reschedules it with the critical-path engine, measures the difference, and throws the copy away.
The impact numbers are observed, not predicted.
Capability honesty
project_health publishes a capability matrix, and the tools honour it. Two things stay false on
the file backend and refuse rather than approximate:
write_native_mpp— no library can author the binary format. Where Microsoft Project is installed, the save is delegated to it and you get a genuine.mpp; where it is not, you get MSPDI and an explanation.level_resources— Microsoft Project's levelling heuristic is unpublished. Any imitation would be a different answer wearing the same name.
Saving over a baseline that already holds data is refused too, unless you ask for it explicitly. A baseline is the record of the original plan that every variance is measured against, and it cannot be recovered from the file afterwards.
Everything else — scheduling, recalculation, dry-run simulation, rescheduling incomplete work, the DCMA Critical Path Test — works everywhere. Who computes the dates is the next section.
Dates: Microsoft Project's own
Where Microsoft Project is installed, Microsoft Project calculates the dates. Recalculating,
rescheduling after a write, dry runs, recovery options, target dates and the DCMA Critical Path Test
all hand the schedule to Project, let it calculate, and take back the dates it computed.
project_health reports it as schedulingEngine: microsoft-project.
Measured, not assumed. On seven real construction schedules — 21 to 5,984 tasks, 8,823 in all counting summaries, with split tasks, work in progress, 9-hour days and Saturday half-days — recalculating through this server reproduced the dates Microsoft Project computes on every task of every schedule, to the minute, and left progress exactly as Project had it. Writes were held to the same standard: a duration change, a percent complete or a new link made through this server and the same edit made by hand in Project produced the same dates and the same progress, task for task, summaries included.
That took more than opening the file in Project. Project's own XML import does not reproduce Project: on a real 126-task schedule, re-opening even Project's own XML export put every task on different dates. These are the causes, and the hand-off to Project handles each:
- Unassigned tasks. A task with no resource still carries a placeholder assignment, and on import Project schedules it against the placeholder resource's calendar instead of the task's. It is left out whenever it carries nothing the task does not already say.
- Split tasks. Work that starts, pauses and resumes keeps its gaps only in the assignment's day-by-day work, so that travels too.
- Work in progress. An in-progress task comes back from an XML import with part of its completed work moved into remaining. So progress is never taken back from that trip; when a write changes it, it changes by Project's own rules — a longer duration keeps the work already done, a new percent starts or finishes the task — and summaries roll it up the way Project does.
- Blank rows. A row inserted in Project and left empty is not a task to Project, but it reads as one dated at the project start, and a summary on a real schedule grew back two years to reach it. It goes over as the blank row it is.
A recalculation of the 4,753-task schedule takes about 20 seconds, most of it inside Project.
If you have Project open, it is used as it is. Microsoft Project is single-instance — any automation, this server's included, lands in the copy you are using — so this server never hides your window, never recalculates or closes your documents, and only ever touches a temporary copy it opened itself, checking before every step that the active document is still that copy. You are left on the document you had active.
Without Microsoft Project
MPXJ reads and writes schedule files but does not schedule them, so there is also a critical-path engine of its own — forward and backward pass, total and free float, all four relation types, lag, constraints, deadlines, actual dates, and each task's working calendar. It is what runs on macOS, Linux, and Windows machines without Project.
⚠️ That engine is not Microsoft Project's scheduler
It reproduces Project exactly on schedules built through this server, not on real imported ones: on four production files it matched Project's own start dates on 100%, 69%, 23% and 23% of tasks. It does not implement task types, effort-driven scheduling, resource-driven dates, manual or split tasks, or elapsed durations. So without Project, an imported schedule is never silently rescheduled — its dates stay Project's until you ask for this engine's explicitly with
schedule_update op='recalculate', which warns you first. Reading, analysis, DCMA-14 and earned value run on the dates the file already holds and are unaffected.
Wiring it to any other client
Claude Desktop, Claude Code and Codex are covered in docs/INSTALL.md. For anything else that speaks MCP over stdio — Cursor, VS Code, your own client:
Registry name: io.github.HorizunGroup/horizun-msproject-mcp (see .mcp/server.json).
Call project_health first in every session — it tells you which backend you are on and what it
can do.
Build and test from source
264 checks, driven over real JSON-RPC against the running server, on Windows and on
Linux. With Microsoft Project installed the suites run with Project calculating the dates, and
project-engine-test.py compares the server against Project doing the same thing by hand — dates,
progress and summaries, task by task — and checks that a Project you have open is left exactly as it
was. The Linux job is the evidence for the headline claim: it runs on a machine with no
JVM and no Microsoft Project.
The acceptance suite builds a construction schedule from nothing and asserts the contracts above: that a dry run commits nothing, that a cycle is refused before it is applied, that a write to an unknown uid is rejected rather than ignored, and that the DCMA Critical Path Test moves the finish date by exactly the delay injected into it.
The scheduler suite is the one that earns trust in the dates. It covers start-to-start,
finish-to-finish and start-to-finish logic, positive and negative lag, hard and soft constraints,
deadlines producing negative float, calendar exceptions actually pushing the schedule out, and a
WBS hierarchy with summary rollup, that an imported schedule is never silently rescheduled, and
full round trips through Primavera XER and PMXML and through a real binary .mpp — the last
written by Microsoft Project itself, read back by MPXJ, with dates, milestone flags, budget codes
and dependencies all intact.
Beyond the suites, the server has been driven through a planner's full working cycle on two production construction schedules — a 5,985-task programme and a 170 MB, 1,937-task one — opening, auditing, baselining, recording progress, measuring earned value and exporting the Power BI dataset, and read against files of up to 7,000 tasks.
The robustness suite is the one that matters for trusting this in a real client: forty writes in flight at once on the same document, hostile paths, absurd page sizes, non-latin names. MPXJ's object model is not thread-safe and an MCP client is free to pipeline calls — unguarded, sixty concurrent writes all failed and left the document unusable. Every document now has its own lock, reentrant because several tools are built on others.
A schedule stays in memory until it is closed, and a 170 MB one costs around 400 MB. Reading many
retires the oldest document that has nothing unsaved; when every open document has unsaved work,
opening another is refused rather than discarding any of it. project_health reports what is open
and what it is costing.
Rebuild the installable package with dotnet pack -c Release.
Formats
Reads .mpp .mpt .mpx MSPDI .xml · Primavera .xer .pmxml · Asta .pp · Planner ·
GanttProject and more, through MPXJ.
Writes MSPDI .xml (Microsoft Project opens it natively) · .mpx · Primavera .xer and
.pmxml · Planner · SDEF · JSON · CSV · Power BI dataset · native .mpp where Microsoft Project
is installed.
Layout
Design rationale and the market benchmark that motivated it: DESIGN-TOOL-SURFACE.md and BENCHMARK-MCP-MSPROJECT.md.
Licence
MIT.