# OpenRouter: Advisor server tool

## Metadata

| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | cap-protocol |
| Document type | Source Dossier |
| Tier | 1 |
| Source title | OpenRouter: Advisor server tool |
| Source URL | https://openrouter.ai/blog/announcements/advisor-server-tool/ |
| Source publisher / author | OpenRouter |
| Source type | blog post |
| Source date (published) | Unknown — not stated |
| Date researched | 2026-10-25 |
| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
| Research method | direct page fetch |
| Confidence | Medium |
| Status | Active |

## Summary

OpenRouter's cross-vendor advisor: any executor model can consult a stronger model mid-generation; the advice returns as a tool result and the executor writes the answer.

## Key findings

- The advisor is 'a consultant, not a ghostwriter': single-turn, no nested tool loop; a tool-carrying sub-agent is a separate tool.
- Parameters: `model`, optional `name`, `instructions`, `stream`; the executor passes a `prompt` describing what it needs help with.
- Safeguards: an `x-openrouter-advisor-depth` header on inner calls and stripping the advisor tool from sub-calls prevent unbounded nesting; consultations are capped per request (number not given).
- Advisor tokens bill at the advisor model's own rates, shown separately from the executor's.
- Claimed use: the 10-20% of requests with architectural decisions or ambiguous edge cases; in a 50-tool-call session the article estimates maybe 2-3 consultations.

## Pros / strengths

Names the safeguards a model-callable model needs: depth marker, tool stripping, per-request cap, separate billing.

## Cons / limitations / caveats

Vendor announcement; the cap value and the 10-20% share are asserted, not measured; a search listing suggested other pages describe it as a sub-agent, so docs may differ.

## Relevance to tai

Blueprint for tai's guard rails if a model-as-tool is added: nested calls get the tool removed, a static per-turn ceiling, and the cost line attributed to the consulted model.

## Changelog

| Date | Change |
|---|---|
| 2026-10-25 | Initial dossier created. |