Hacktoberfest 2026: le issue che i maintainer hanno segnato per ottobre, aperte e adatte ai principianti. Sfoglia le issue Hacktoberfest

No structured way to signal a tool's refusal, distinct from success or a schema-validation error

Aperta
  • Qualcosa non va?
#282 10 commenti 0 reazioni 0 assegnatari Vedi su GitHub

I maintainer di solito rispondono entro 1 giorno

Nessuno ha ancora preso questa issue.

Valutazione

Difficoltà
5/5
Tempo stimato
Più di una settimana
Idoneità per principianti
30/100
Tipo di issue
Funzionalità
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
javascript
Ambito
api

Direzione di ricerca

Start by reading the WebMCP spec sections that define execute() results and tool errors, then review the seven-comment discussion for existing proposals or objections. Work out whether a structured refusal outcome fits the spec’s result model and how callers should distinguish it from success and schema-validation failure; done means the issue reaches a decided, specified behavior.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

backwards-compatibility concerns enhancement

Filing this from real friction hit building three apps for the WebMCP Challenge (one of them, Consequence, is built specifically around this issue).

The situation

execute() returns { content: [{ type: "text", text }] } regardless of whether the tool succeeded, was refused on purpose, or failed. There's no structured field distinguishing "I did the thing" from "I'm declining to do the thing, on purpose, and here's why."

We needed this because some of our tools enforce a real permission boundary: an agent is allowed to fill most fields on a form, but a few (attestations, signatures) can only be set by a human. When an agent calls our answer_question tool on one of those fields, the tool needs to refuse, clearly and on purpose, not silently no-op and not throw a generic error.

What we did instead

We return a normal-shaped success result whose text is a plain-language refusal message ("Refused: this field requires the human's own action"), and rely on the calling agent to read and respect that text. It works, but it's a convention we invented, not something the spec gives any structure to. An agent framework has no principled way to tell "the tool succeeded and this is the answer" apart from "the tool declined and this is why" without parsing prose.

Why this seems worth a spec-level answer

  • A refusal is a different kind of outcome than a normal result, and calling code (or a UI showing tool-call history, which several of our apps do) benefits from being able to render it differently without string-sniffing.
  • It's different from a schema-validation failure (which the runtime already rejects before execute even runs) — this is a tool voluntarily declining a well-formed, schema-valid call, because of business logic the schema can't express.
  • Multiple entries in the awesome-webmcp list implement permission/authorization patterns where this would apply (ours included), so it's probably a recurring need, not a one-off.

Happy to be pointed at existing discussion if this has already been considered and rejected — didn't find one searching open issues.

Lingua principale
Bikeshed
Stelle
4.7k
Fork
328
Merge medio
2g 15h
PR unite (30g)
16

Preparare l'ambiente

Questo progetto non fornisce container di sviluppo, Dockerfile né guida per i contributori, quindi l'ambiente è a tuo carico: parti dal suo README e consulta la nostra guida al primo contributo per i passaggi generali.

Come iniziare

  1. Leggi tutta la issue e poi la guida ai contributi del progetto.
  2. Commenta sulla issue per dire che te ne occupi tu — evita che due persone facciano lo stesso lavoro.
  3. Fai un fork del repository e lavora su un branch.
  4. Apri una pull request che faccia riferimento al numero della issue.

Altre issue di webmachinelearning/webmcp

Tutte le issue di webmachinelearning/webmcp

Issue simili

Altre issue su Backend & API Design

Ricevi le nuove issue nella tua casella

Un breve riepilogo di issue GitHub adatte ai principianti.