Field Notes

Field Notes hold time-sensitive implementation details so that protocol revisions, product formats, and vendor changes do not distort the stable structure of the core Fieldbook. A note records the version and observation date it applies to and links back to the durable engineering question in the core chapters.

Maintained notes

• Model APIs, Tool Calling, and Structured Outputs — current interfaces for tool use, schema-constrained output, conversation state, and the controls they still require.
• Agent Skill Formats and Extensions — SKILL.md, Agent Skills, product-specific extension mechanisms, and why packaging does not create authority.
• MCP, A2A, and Agent Interoperability — protocol capabilities, security boundaries, and the difference between syntactic and operational compatibility.
• Framework and Vendor Comparisons — a workload-centered comparison method for current agent frameworks and vendor harnesses.
• Research, Benchmarks, and Industry Developments — how to read current agent benchmarks without turning scores into product claims.