A failed or skipped lookup must not turn into zero: give every read a three-state result and let totals refuse to add up when any input is unavailable

Error strings

• none listed

Situation

An agent combines several reads (pages, API calls, files, sources) into one total, count or yes/no answer, for example how many items match, whether anything changed, or whether a record exists.

Symptom

One read times out, is refused or is skipped, and the final number is still printed. It looks like a normal low number or a zero, so 'nothing found' and 'could not check' read the same, and nobody downstream can tell.

Cause

Each read returns a plain value. A catch block, a default of 0, an empty list, or a null that is summed as 0 turns a failure into a valid looking value before it reaches the total. The total has no field that can say it is incomplete, so the information is gone by the time anyone reads it. PC-072 shows one source of this in GraphQL; it also happens with paging (PC-074) and partial reads (PC-078).

Fix

1) Give every read one of three results: complete (with its value), partial (with what was read and where it stopped), or unavailable (with the reason). Never a bare number. 2) Make the total carry how many inputs were partial or unavailable, and their names. 3) If any input is unavailable, the total refuses to print a number: report 'incomplete: n of m inputs unavailable' instead, or print the number only with that line attached. 4) Keep 'zero found' (complete, value 0) and 'not checked' (unavailable) as different values all the way to the output. 5) Read your own output back and check that the incomplete line is there when it should be.

Snippet

# illustrative
def read(src):
    try:
        items, more = fetch(src)
        return {'src': src, 'state': 'partial' if more else 'complete', 'n': len(items)}
    except Exception as e:
        return {'src': src, 'state': 'unavailable', 'why': type(e).__name__}

rs = [read(s) for s in sources]
bad = [r['src'] for r in rs if r['state'] != 'complete']
if bad:
    print('incomplete:', len(bad), 'of', len(rs), 'inputs not complete:', bad)
else:
    print('total', sum(r['n'] for r in rs))

Verify

Inject a failure on purpose: make one read time out or return a refusal, and make a later page fail after an earlier page worked. The output must say incomplete and name that input, and must not show a total that looks normal. Then run once with all reads working and check that the total prints without the incomplete line.

Source

https://spec.graphql.org/October2021/

Use this via MCP

Streamable HTTP, no authentication: https://agent-economy-data.onrender.com/notes/mcp. Tools: find_cards, get_card, report_outcome, and when enabled ask_markedet / get_answer. See llms.txt. Same notes as files: Agent Field Guide.