Perseus

Perseus (legal name Efficient Systems Inc.) is an applied AI lab focused on semantic search in latent spaces, founded by Samrath Chadha and backed by Y Combinator (Fall 2025 batch). Its first product is a retrieval engine that grounds coding agents in real code: developers and agents describe the code they are looking for in plain English and Perseus returns ranked file:line results with snippets in seconds, indexing the working tree (including uncommitted edits) so models like Claude Code, Cursor, and Codex can find the right context before editing. Rather than a public REST API, Perseus ships a first-party CLI (installed via a curl/PowerShell one-liner, as a PyInstaller binary or uv wheel), a provider-published Agent Skill, and a Factory Droid plugin, all under the efficientsystemsinc GitHub organization. The developer surface — docs, console, pricing, and blog — is live; there is no OpenAPI, MCP server, or /.well-known discovery document published as of this pass.

Perseus is profiled on the APIs.io network. Tagged areas include Company, Artificial Intelligence, Developer Tools, Code Search, and Semantic Search.

Perseus’ developer surface includes documentation, getting-started guide, pricing, engineering blog, signup flow, support, CLI, and 8 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

28.4/100 thin ▬ flat Agent 6/100 agent aware saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreemium

0 APIs 1 Agent Skills

Company Artificial Intelligence Developer Tools Code Search Semantic Search Coding Agents AI AgentsLatent SpaceCLI Agent Skills Y Combinator

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 28.4/100 · thin

Contract Quality 0.0 / 21

Developer Ergonomics 10.9 / 17

Access Clarity 9.4 / 17

Operational Transparency 0.3 / 11

Contract Governance 0.0 / 10

Discoverability 4.1 / 9

Regulatory Posture 1.6 / 15

Agent readiness — 6/100 · agent aware

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document
MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0

11 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 0.0 — up to +25.0 composite points
Operational Transparency scores 2.6 — up to +12.7 composite points
Contract Governance scores 0.0 — up to +12.0 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/perseus/apis.yml: open an issue on github.com/api-evangelist/perseus to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

Agent Skills

measured — observed by APIs.io (published)

Agent Skills 1

Packaged agent skills for driving this provider's APIs from an AI assistant.

perseus

AGENT SKILL

Perseus API pricing

Prices published by Perseus, read 2026-10-07 from perseus.computer/pricing.

Plan	Price
Demo week	$5/ one-time/ 7 days Includes: 250 queries, 1 indexed repository, 100k indexed LOC, 20 ask calls, 7 days memory retention
Developer	$20/ seat/ month Includes: 2,000 queries / month, 3 indexed repositories, 2M indexed LOC, 200 ask calls / month, 90 days memory
Scale	$100/ seat/ month Includes: 5,000 queries / month, 15 indexed repositories, 25M indexed LOC, 1,500 ask calls / month, Unbounded

Plan details, limits and sources →

Pricing Plans 1

Published pricing tiers and plan structures.

Perseus Plans Pricing

3 plans

PLANS

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Perseus Authentication

token · 1 scheme

SECURITY

Perseus Domain Security

TLSv1.3

SECURITY

Resources

Get Started 3

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

DeveloperPortal

DeveloperPortal

SignUp

SignUp

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgentSkill

AgentSkill

Build 3

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

CLI

CLI

Packages

Packages

Access & Security 2

Authentication, authorization, and security posture

Authentication

Authentication

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 2

Pricing, plans, and the legal terms of use

Plans

Plans

Pricing

Pricing

Company 2

The organization behind the API

Website

Website

Blog

Blog

Source (apis.yml)

aid: perseus
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  - authentication
  - security
  generated: '2026-11-06'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/perseus.png
name: Perseus
description: 'Perseus (legal name Efficient Systems Inc.) is an applied AI lab focused on semantic search in latent spaces,
  founded by Samrath Chadha and backed by Y Combinator (Fall 2025 batch). Its first product is a retrieval engine that grounds
  coding agents in real code: developers and agents describe the code they are looking for in plain English and Perseus returns
  ranked file:line results with snippets in seconds, indexing the working tree (including uncommitted edits) so models like
  Claude Code, Cursor, and Codex can find the right context before editing. Rather than a public REST API, Perseus ships a
  first-party CLI (installed via a curl/PowerShell one-liner, as a PyInstaller binary or uv wheel), a provider-published Agent
  Skill, and a Factory Droid plugin, all under the efficientsystemsinc GitHub organization. The developer surface — docs,
  console, pricing, and blog — is live; there is no OpenAPI, MCP server, or /.well-known discovery document published as of
  this pass.'
url: https://raw.githubusercontent.com/api-evangelist/perseus/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
x-tier: stub
x-tier-reason: portfolio-lead
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-20'
tags:
- Company
- Artificial Intelligence
- Developer Tools
- Code Search
- Semantic Search
- Coding Agents
- AI Agents
- Latent Space
- CLI
- Agent Skills
- Y Combinator
x-enrichment:
  date: '2026-07-20'
  status: enriched
  artifacts_added: 6
  pass: local-v1
apis: []
common:
- type: Plans
  url: plans/perseus-plans-pricing.yml
- type: Website
  url: https://perseus.computer
- type: Documentation
  url: https://perseus.computer/docs
- type: GettingStarted
  url: https://perseus.computer/docs
- type: DeveloperPortal
  url: https://perseus.computer/console
- type: Pricing
  url: https://perseus.computer/pricing
- type: Blog
  url: https://perseus.computer/blog
- type: SignUp
  url: https://perseus.computer/console/onboarding?plan=developer_monthly
- type: Support
  url: mailto:hello@perseus.computer
- type: GitHubOrganization
  url: https://github.com/efficientsystemsinc
- type: CLI
  url: cli/perseus-cli.yml
- type: AgentSkill
  url: skills/perseus-code-search.md
- type: Packages
  url: packages/perseus-packages.yml
- type: Authentication
  url: authentication/perseus-authentication.yml
- type: DomainSecurity
  url: security/perseus-domain-security.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io

Perseus API — frequently asked questions

How do I authenticate with the Perseus API?

Perseus uses bearer-token authentication (token · 1 scheme). The details are profiled on APIs.io as Perseus Authentication.

How much does the Perseus API cost?

Perseus publishes its prices; its Demo week plan is $5/ one-time/ 7 days as of 2026-10-07. APIs.io lists 3 pricing plans for Perseus, with each plan's price, limits and inclusions under Pricing on this page.

Is the Perseus API ready for AI agents?

Perseus has a Kin Score of 28.4 out of 100 (thin) and an Agent Readiness score of 6.1 (agent-aware), scored by API Evangelist on 2026-11-06.

Work with this as data

Every provider here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for providers

9 MCP tools reach this

find_providersBrowse and filter every provider in the catalog.
get_provider_artifactsEvery artifact this provider publishes, grouped by type.
get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
get_provider_ratingPRO — composite, band, trend and facet scores.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

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How their score was established

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