51 lines
2.3 KiB
Markdown
51 lines
2.3 KiB
Markdown
# MCP specification 2025-06-18: Sampling (model preferences)
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## Metadata
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| Field | Value |
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| Institute | Molodetz Institute — Research & Retrieval Division |
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| Subject | cap-protocol |
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| Document type | Source Dossier |
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| Tier | 1 |
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| Source title | MCP specification 2025-06-18: Sampling (model preferences) |
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| Source URL | https://modelcontextprotocol.io/specification/2025-06-18/client/sampling |
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| Source publisher / author | Model Context Protocol project |
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| Source type | standard |
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| Source date (published) | 2025-06-18 |
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| Date researched | 2026-10-25 |
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| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
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| Research method | direct page fetch |
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| Confidence | High |
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| Status | Active |
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## Summary
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The MCP feature by which a server asks the client's model for a completion, notable here for its model-selection abstraction.
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## Key findings
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- A server cannot simply request a model by name because the client may not have that model or may prefer another provider's equivalent.
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- Preferences combine three normalized priorities, `costPriority`, `speedPriority`, `intelligencePriority` (0 to 1), with optional `hints`.
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- Hints are substrings that match model names flexibly, are evaluated in order, MAY map to equivalent models from other providers, and are advisory: 'clients make final model selection'.
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- Example: hints `claude-3-sonnet` then `claude`, with cost 0.3, speed 0.8, intelligence 0.5.
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- Humans in the loop: there SHOULD always be a way to deny sampling requests; clients SHOULD show requests and responses for review, rate-limit, and respect hints.
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## Pros / strengths
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A finished, widely implemented answer to 'how does a caller name a model without knowing the callee's catalog': substring hints plus capability priorities, resolved by the owner of the models.
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## Cons / limitations / caveats
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Priorities are unitless hints; the spec does not say how a client turns them into a choice.
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## Relevance to tai
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Matches the shape of tai's fuzzy `@model` resolution (substring-style hints resolved by the side that knows the catalog). A tool input of `hints` plus optional priorities is a precedent for `ask_agent(model_hint=...)`. Human-in-the-loop rules inform the approval default.
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## Changelog
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| Date | Change |
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| 2026-10-25 | Initial dossier created. |
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