[Gap]: Composite tools guide: output spec not documented

[danbarr]

Summary

The composite tools guide doesn't document the output section of composite tool definitions at all. The only way to discover that composite tools can define structured output mappings is to read the full CRD spec reference.

What's missing

The guide should cover:

• The output block and its properties / required structure
• How to map step results to output properties using value with template expressions
• The difference between extracting scalar fields (fromJson + field access) vs passing through entire responses (raw .output.text as a string)
• Typed output properties and their coercion behavior (e.g. type: integer can't handle null)
• The default field on output properties
• How defaultResults on conditional steps feeds into output references

Without this, users have to reverse-engineer the output spec from the CRD reference, which is a significant barrier — especially since the output mapping is where most of the fromJson and template expression complexity lives.

Related

• [Gap]: Composite tools guide: gaps found when building a real workflow #627 — other composite tools guide gaps (JSON text handling, elicitation decline, defaultResults structure)
• Composite tools: elicitation message doesn't expand template expressions toolhive#4312 — bug: elicitation messages don't expand templates