SpicyAPI’s Claude Sonnet 4.5, 5 and 5.5 API version guide starts from a point most model-migration posts skip: “An editing integration carries more than a model name: it may depend on a sampling setting, a forced function call or a reply parser.” All four Sonnet versions share one /v1/chat/completions request shape on SpicyAPI, and they are still four different contracts. Sonnet 5 and 5.5 reject temperature, top_p and top_k; 5.5 also rejects a forced tool_choice; only 5.5 writes past 64,000 output tokens, with a 128,000 ceiling. The blunt version: “Changing the model ID alone breaks a request.”
The prices are SpicyAPI’s hosted rates, in USD per million tokens, and the post discloses that it sells access to every model it compares. Sonnet 5 is listed at $1.90 in and $9.50 out, Sonnet 5.5 at $2 and $10, Sonnet 4.6 at $3 and $15. Its cost example leans on a roughly 30% tokenizer increase it attributes to Anthropic’s migration guide, and it says plainly the resulting 9% saving “is not fixed for every document.” What survives the sales context is the engineering: unsupported fields return 400 unsupported_parameter before anything is charged, so keep a per-model allowlist instead of one shared parameter object, and validate the reply because 5.5 “can skip the function.”
SpicyAPI on apis.io carries 5 API pages, and the guide lives on two of them. The SpicyAPI OpenAI Compatible API is the chat completions endpoint every example calls, and the SpicyAPI Models API is the model contract an agent reads first, which the post exposes through the CLI and the spicyapi_model_get MCP tool. The agentic access profile counts 24 operations, 14 acting.
The measurement mostly agrees with the post. SpicyAPI scores 72.0 on the Kin Score, exemplar, with access clarity at 92.1 and operational transparency at 86.8. Agent Readiness is 37.3, with idempotency and error semantics lit, and the sample code does send an Idempotency-Key and parse the documented error. The weak facet is contract governance at 22.0, and OpenAPI examples and agent skills are unlit, even though the post tells readers to install an official SpicyAPI Skill. The per-version table in this blog post is the most precise contract SpicyAPI publishes for Sonnet. It belongs in the Models API response, where an agent would find it without reading a 13-minute article.