# AgentStack MCP: one deterministic reasoning stack for AI agents (simulate + decide + compute)

> Source: <https://dev.to/datanestdigital/agentstack-mcp-one-deterministic-reasoning-stack-for-ai-agents-simulate-decide-compute-597p>
> Published: 2026-08-11 12:30:22+00:00

*The fourth in a suite of deterministic MCP servers for AI agents — and the one that ties the first three together.*

Over the last stretch I shipped three focused, deterministic MCP servers:

They're great on their own, but agents kept needing all three in the same task — and installing three servers, juggling three keys, and hand-gluing their outputs is friction. So here's **AgentStack MCP**: one endpoint, one key, all three — plus composite tools that chain them.

```
{ "mcpServers": { "agentstack": {
    "type": "http", "url": "https://agentstack-mcp.pages.dev/mcp" } } }
```

Free tier: no key, 20 calls/day. The tools are namespaced so an agent always knows which engine it's calling:

`sim_*`

— ScenarioSim (run, sensitivity, break-even, compare, templates)`decide_*`

— DecisionMatrix (decide, score, sensitivity, compare_two, methods)`calc_*`

— PrecisionCalc (metrics, currency, NPV, IRR, loan, depreciation, …)These chain the engines to do reasoning **no single server can**, deterministically end-to-end:

** evaluate_options_with_scenarios** (simulate → decide) — project each option as its own scenario, then rank the

```
{ "name": "evaluate_options_with_scenarios", "arguments": {
  "template": "saas_growth", "horizon": 12,
  "options": [
    { "name": "Aggressive", "inputs": { "new_customers_per_period": 60, "churn_rate": 0.05 } },
    { "name": "Lean",       "inputs": { "new_customers_per_period": 20, "churn_rate": 0.02 } }
  ],
  "criteria": [
    { "metric": "ending_mrr", "weight": 3, "direction": "benefit" },
    { "metric": "total_churned_customers", "weight": 1, "direction": "cost" }
  ]
} }
```

** plan_to_valuation** (simulate → compute) — project a plan, then value its cash-flow line: NPV, IRR, undiscounted total.

** stress_test_decision** (simulate × decide) — stress one scenario assumption across every option and report how often the chosen option survives (robustness) and where it flips.

Bundling 24 tools risks drowning an agent's tool-selection. So the endpoint takes a `?profile=`

filter:

```
https://agentstack-mcp.pages.dev/mcp?profile=finance
```

`finance`

→ `calc_*`

+ `plan_to_valuation`

`decision`

→ `decide_*`

+ the two decision composites`simulation`

→ `sim_*`

+ all composites`all`

(default) → everything`io.github.inity13/agentstack-mcp`

If your agents plan, choose, and do the numbers, give them one calculator that does all three — and never drifts. Feedback welcome.