---
title: Design-time capabilities
editUrl: https://github.com/Cratis/Chronicle.Mcp/edit/main/Documentation/design-time/index.md
description: The design-time tools turn a plain-language request into Chronicle artifacts — read models, projections, audits, and catalogs — grounded in the store's…
---

The design-time tools turn a plain-language request into Chronicle artifacts — read models, projections, audits, and catalogs — grounded in the store's real schema. They are read-only against the store and generative against your codebase: nothing is written to the store, and generated code comes back as a proposal you review. See [How it works](/chronicle-mcp/concepts/) for the principle behind them.

## Capabilities

| Capability | Tool | Use it to |
| --- | --- | --- |
| [Describe the system](/chronicle-mcp/design-time/describe-system/) | `describe_system` | Deduce what the system is and is for — entities, lifecycles, read surfaces, automations — and tell its story. |
| [Suggest the next event types](/chronicle-mcp/design-time/suggest-next-event-types/) | `suggest_next_event_types` | Find lifecycle gaps and get grounded suggestions for the event types to introduce next. |
| [Ad-hoc projection](/chronicle-mcp/design-time/ad-hoc-projection/) | `run_ad_hoc_projection` | Answer "show all X with all details" by folding events into current state on demand — nothing registered. |
| [Describe an event type](/chronicle-mcp/design-time/describe-event-type/) | `describe_event_type` | Read an event type's real fields and types — the grounding primitive the others build on. |
| [Read-model scaffolding](/chronicle-mcp/design-time/read-model-scaffolding/) | `scaffold_read_model` | Turn a set of event types into a reviewable read model + projection, grounded in their schema. |
| [Unconsumed-event audit](/chronicle-mcp/design-time/unconsumed-event-audit/) | `audit_unconsumed_event_types` | Find events nothing reads, and consumers pointing at event types that no longer exist. |
| [Event catalog](/chronicle-mcp/design-time/event-catalog/) | `generate_event_catalog` | Produce a living data dictionary — every event, its fields, and its consumers. |
| [Causal trace](/chronicle-mcp/design-time/causal-trace/) | `explain_causal_trace` | Turn an event source's raw log into a "what happened and why" narrative. |

## Prompts

Beyond tools, the server exposes MCP prompts that package whole workflows — clients that surface prompts (for example as slash commands) can offer them directly:

| Prompt | What it does |
| --- | --- |
| `describe_system` | Describe what the system is and is for, and tell its story. |
| `suggest_next_event_types` | Propose the next event types, refined with domain knowledge. |
| `query_system` | Answer a natural-language question ("show all employees with all details") with an ad-hoc projection. |

## How an agent combines them

A typical flow chains a few tools. To answer *"Show all employees with all details"* an agent might:

1. Understand the system with [describe the system](/chronicle-mcp/design-time/describe-system/) — which entities exist and which event types carry which facts.
2. Fold the relevant event types into current state with an [ad-hoc projection](/chronicle-mcp/design-time/ad-hoc-projection/) and present the result.
3. If the question keeps coming back, propose a permanent read model with [read-model scaffolding](/chronicle-mcp/design-time/read-model-scaffolding/).

Because the tools return structured data rather than prose, the agent does the natural-language reasoning while the store supplies the facts.

## Roadmap

The [capability hand-off](https://github.com/Cratis/Chronicle.Mcp) sketches ten design-time capabilities. The tools above cover the grounding-and-generation core plus system understanding, evolution suggestions, and ad-hoc querying. The remaining ideas — projection-vs-reducer advice, consistency-boundary (DCB) advice, schema-evolution assistance, spec scaffolding, and constraint suggestions — build on the same introspection pipeline and are candidates for future releases.