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Letta vs Vespa

Letta scores higher on the AgentReady, 72/100 against 56/100. They differ on 7 of the 41 signals. Which ones decides whether an agent can adopt them without a person watching.

What each one is

Letta. Letta is an AI research lab in San Francisco building machines that learn.

Vespa. Vespa.ai develops the Vespa AI Search Platform, a distributed serving engine that unifies retrieval, ranking, machine learning inference, and real-time serving for business-critical AI applications.

Where Letta is ahead

Letta passes mcp discoverable, and Vespa does not. That is discover, whether an agent can find the product at all without being told it exists.

It also holds understand: authentication documented. Vespa misses it.

And on adopt, agent-compatible signup flow and mcp integration available. Vespa misses those.

Finally, on operate, structured, predictable output and agent compatibility verified. Vespa misses those.

Where Vespa is ahead

Vespa passes structured api reference, and Letta does not. That is understand, whether an agent can read the docs and work out how the API behaves before calling it.

What neither does

Both fail openapi / spec quality, request examples provided, response examples provided, errors and status codes documented, no mandatory sales call, programmatic credential creation, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable. If your agent needs any of those, you will be building it yourself either way.

Score, pillar by pillar

The AgentReady splits into four pillars, scored separately, because a product can be easy to find and still impossible to adopt.

Discover. Letta leads 100 to 87. Letta misses nothing; Vespa misses mcp discoverable.

Understand. Vespa leads 46 to 38. Letta misses structured api reference, openapi / spec quality, request examples provided, response examples provided, errors and status codes documented; Vespa misses openapi / spec quality, authentication documented, request examples provided, response examples provided, errors and status codes documented.

Adopt. Letta leads 81 to 55. Letta misses no mandatory sales call, programmatic credential creation; Vespa misses no mandatory sales call, agent-compatible signup flow, programmatic credential creation, mcp integration available.

Operate is whether an agent can run against it in production and recover when a call fails. Letta leads 67 to 35. Letta misses machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable; Vespa misses structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable, agent compatibility verified.

Pricing

Letta starts at $0/mo and has a free tier. Vespa starts at $0.05/hour with no free tier.

Signal by signal

Which to pick

Letta clears more of the signals an agent needs, so it is the safer default for unattended use. Full profiles: Letta and Vespa. Alternatives to each: Letta, Vespa.

An agent can fetch this as data: POST /v1/compare {"slugs": ["letta", "vespa"]}