Perseus

What it does

Perseus is Lettria’s platform for developers and technical teams building graph agents. It creates ontologies from domain data and supports building and versioning knowledge graphs with input from business experts. An ontology editor and evaluation tools help teams inspect the graph structure before using it in an AI application.

The pricing page lists graph and ontology building, an ontology editor and evaluation. Its free Developer tier has a 30 KB maximum input size, five graph builds and one ontology build per 30 days. Plus lists a 1 MB maximum input size, 3,000 graph builds and 300 ontology builds per 30 days. Enterprise is custom. These published limits make the free tier bounded rather than unrestricted. The page also lists Plus at $0.01 per PCU, but does not define PCU; confirm what consumes a unit and how usage is billed.

Use the Perseus web application or documented SDK-level access to build custom knowledge graphs. Start through the official Try Perseus link and getting-started documentation. Confirm SDK prerequisites, accepted inputs and export formats for your use case. Lettria’s separately scoped GraphRAG services have their own pilot and enterprise terms.

What it can do

• Generate ontologies from domain data
• Build knowledge graphs
• Version knowledge graphs
• Edit ontologies
• Evaluate ontologies
• Build graph agents on graph infrastructure

Before you choose

• Free and Plus have input-size and build allowances; confirm how they fit your data.
• PCU is the published Plus usage unit but its definition needs confirmation.
• GraphRAG service engagements are distinct from Perseus platform tiers.

Listed under

• Coding
• MCP and agent tools
• Data infrastructure
• Developers
• Enterprise AI
• Graphrag
• Knowledge graph
• Ontology

Get started

The official site links to the Perseus app; the pricing page lists a free Developer tier.

1. Open the Perseus app through the official Try Perseus link.
2. Create an account or sign in to access the app; the pricing page lists a free Developer tier.
3. Consult the Perseus getting-started documentation for technical orientation.

The page lists Developer as free, Plus pay-per-use and Enterprise custom. It does not specify the PCU billing cadence or define the unit. The page separately describes scoped, annually invoiced GraphRAG engagements; those terms are not presumed to apply to Perseus.

Source: lettria.com/pricing-lettria, checked 1 Nov 2026. Prices can change; check before you buy.

Sources for this overview

Product pages, documentation, and pricing checked 1 Nov 2026. Each source supports part of the overview; availability and prices can change.

• Document intelligence for regulated industries.- Lettria ↗www.lettria.com
• Pricing ↗www.lettria.com
• Contact ↗www.lettria.com
• Document intelligence for regulated industries.- Lettria ↗www.lettria.com
• Alfa Laval: Empowering engineering experts with an assistant powered by GraphRAG ↗www.lettria.com

Company website

lettria.com: product, pricing and policy pages

YC directory mirror

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Human review

Checked by a person

knowledge_base

manual_review

Last checked 1 Nov 2026. Every field keeps its source and date; unknown means we couldn’t confirm it.