Architectural decision (ADR-005) for a multi-model, multi-provider, and tool strategy, addressing compatibility and routing complexities.
Raw Developer Origin & Technical Request
GitHub Issue
Mar 27, 2026
# ADR-005: Multi-Model, Multi-Provider, and Tool Strategy
**Status:** Draft
**Date:** 2026-03-27
**Deciders:** Jeremy McSpadden
**Related:** ADR-004 (capability-aware model routing), ADR-003 (pipeline simplification), [PR #2755](github.com/gsd-build/gsd-2/p...
## Context
PR #2755 lands capability-aware model routing (ADR-004), extending the router from a one-dimensional complexity-tier system to a two-dimensional system that scores models across 7 capability dimensions. GSD can now intelligently pick the best model for a task from a heterogeneous pool.
But model selection is only one piece of the multi-model puzzle. The system now faces a set of structural gaps that become more pressing as users configure diverse provider pools:
### 1. Tool compatibility is assumed, not verified
Every registered tool is sent to every model regardless of provider. The `pi-ai` layer normalizes tool schemas per provider (Anthropic `tool_use`, OpenAI `function`, Google `functionDeclarations`, Bedrock `toolSpec`, Mistral `FunctionTool`), but there is no mechanism to express that:
- A model may not support tool calling at all (older/smaller models, some local models)
- A provider may not support certain schema features (Google Gemini doesn't support `patternProperties`; `sanitizeSchemaForGoogle()` patches this silently)
- Some tools produce image content in results that not all models can consume
- Tool call ID formats differ across providers (Anthropic: 64-char alphanumeric; O...
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