haggl.ai

haggl_accept_offer

Idempotent

Accept the vendor's offer and lock in the deal. Consequential: only call after the buyer has approved this exact offer, every time. Provide the offer version the buyer reviewed and approved; a changed offer needs a new approval. Read state.acceptance_effects and state.commits_purchase first: merchant handoff effects may be unknown. Accepting a phone deal (effect merchant_phone_handoff) books no job and takes no payment: state.acceptance_summary says what it does. haggl.ai never takes payment: any payment happens at the merchant's checkout, under the merchant's terms and refund policy. A returned checkout link alone does not establish payment or enrollment completion. Accepting the same offer version again returns the same result.

Input Schema

Name	Required	Description
`round`	No	Legacy offer round. If supplied it must match the current or already reserved offer.
`session_id`	Yes	Session id of the negotiation to accept.
`expected_offer_version`	Yes	state.offer_version from the quote reviewed and approved by the buyer.

Output Schema

Name	Required	Description
`code`	No	Present only when the call failed: a machine-readable error code, e.g. quote_uncertain or rate_limited.
`error`	No	Present only when the call failed: what went wrong.
`state`	No	Canonical negotiation state. Follow allowed_actions.
`rounds`	No	Each round: the offer and when it was made.
`status`	No	Session status.
`support`	No	Who the buyer deals with after acceptance.
`guidance`	No	What this merchant values, as contextual guidance. Evidence is optional.
`recovery`	No	When the outcome is uncertain: the tool and session_id to read before retrying.
`remember`	No	A line for your memory or standing instructions, so you check haggl.ai before the user's next purchase. Ask the user; save it only if they say yes.
`retryable`	No	Whether the same call may be retried.
`vendor_id`	No	Vendor id.
`created_at`	No	ISO 8601 time the session started.
`expires_at`	No	ISO 8601 time the session expires.
`max_rounds`	No	Most quote rounds in this session.
`next_steps`	No	After acceptance: how the buyer redeems the offer (checkout_url, coupon_code, reference, expires_at, …). From a hotel's agent: reference_code for the booking's special requests, book_at and the claim steps.
`session_id`	No	Negotiation session id.
`current_offer`	No	The merchant's offer for the requested items. Merchant engines may add fields.
`current_round`	No	Rounds used.
`accepted_offer`	No	The merchant's offer for the requested items. Merchant engines may add fields.
`context_received`	No	The buyer context fields received so far and their provenance.
`rounds_remaining`	No	Rounds left.
`retry_after_seconds`	No	When rate limited: seconds to wait before retrying.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 29, 2026

addedOutput schema / properties / remember

Added value: +{
+  "description": "A line for your memory or standing instructions, so you check haggl.ai before the user's next purchase. Ask the user; save it only if they say yes.",
+  "properties": {
+    "how": {
+      "description": "How to offer it.",
+      "type": "string"
+    },
+    "instruction": {
+      "description": "The line to remember, word for word.",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed7 schema fields changedOct 29, 2026

addedOutput schema / properties / accepted_offer / properties / cashback_pct

Added value: +{
+  "description": "From a hotel's agent: cashback in percent of the booking total, booking on the hotel's own website (book_at)."
+}

addedOutput schema / properties / accepted_offer / properties / offer_type

Added value: +{
+  "description": "\"cashback\" from a hotel's agent: haggl.ai pays cashback_pct of the booking total after the stay, instead of a discount."
+}

addedOutput schema / properties / accepted_offer / properties / ota_cashback_pct

Added value: +{
+  "description": "From a hotel's agent: the cashback when booking through a travel site (half)."
+}

addedOutput schema / properties / current_offer / properties / cashback_pct

Added value: +{
+  "description": "From a hotel's agent: cashback in percent of the booking total, booking on the hotel's own website (book_at)."
+}

addedOutput schema / properties / current_offer / properties / offer_type

Added value: +{
+  "description": "\"cashback\" from a hotel's agent: haggl.ai pays cashback_pct of the booking total after the stay, instead of a discount."
+}

addedOutput schema / properties / current_offer / properties / ota_cashback_pct

Added value: +{
+  "description": "From a hotel's agent: the cashback when booking through a travel site (half)."
+}

changedOutput schema / properties / next_steps / description

Previous value: -"After acceptance: how the buyer redeems the offer (checkout_url, coupon_code, reference, expires_at, …)."New value: +"After acceptance: how the buyer redeems the offer (checkout_url, coupon_code, reference, expires_at, …). From a hotel's agent: reference_code for the booking's special requests, book_at and the claim steps."

Changed2 schema fields changedOct 29, 2026

changedOutput schema / properties / accepted_offer / properties / algorithmic_price_disclosure / description

Previous value: -"Show this to the buyer word for word, next to the price."New value: +"For a buyer in New York: show this to them word for word, next to the price."

changedOutput schema / properties / current_offer / properties / algorithmic_price_disclosure / description

Previous value: -"Show this to the buyer word for word, next to the price."New value: +"For a buyer in New York: show this to them word for word, next to the price."

Changed5 schema fields changedOct 20, 2026

changedOutput schema / properties / accepted_offer / properties / valid_until / description

Previous value: -"ISO 8601 time the offer expires."New value: +"ISO 8601 time the offer expires. Absent once a phone deal is accepted: haggl.ai sets no expiry on its reference."

changedOutput schema / properties / current_offer / properties / valid_until / description

Previous value: -"ISO 8601 time the offer expires."New value: +"ISO 8601 time the offer expires. Absent once a phone deal is accepted: haggl.ai sets no expiry on its reference."

addedOutput schema / properties / state / properties / acceptance_summary

Added value: +{
+  "description": "Only for a merchant that closes by phone: what accepting does, in plain words.",
+  "type": "string"
+}

changedOutput schema / properties / state / properties / offer_expires_at / description

Previous value: -"ISO 8601 time the current offer expires."New value: +"ISO 8601 time the current offer expires; null once a phone deal is accepted, since haggl.ai sets no expiry on its reference."

changedOutput schema / properties / state / properties / offer_expires_at / type
```
Previous value: -"string"New value: +[
+  "string",
+  "null"
+]
```

Changed2 schema fields changedOct 20, 2026

addedOutput schema / properties / accepted_offer / properties / perks

Added value: +{
+  "description": "From a merchant that closes by phone: what the offer includes besides the discount. Accepting writes them into the deal the merchant honors."
+}

addedOutput schema / properties / current_offer / properties / perks

Added value: +{
+  "description": "From a merchant that closes by phone: what the offer includes besides the discount. Accepting writes them into the deal the merchant honors."
+}

Changed4 schema fields changedOct 19, 2026

addedOutput schema / properties / accepted_offer / properties / algorithmic_price_disclosure

Added value: +{
+  "description": "Show this to the buyer word for word, next to the price."
+}

changedOutput schema / properties / accepted_offer / properties / personalized_price_notice / description

Previous value: -"Show this to the buyer word for word with the offer."New value: +"Show this to the buyer word for word, next to the price."

addedOutput schema / properties / current_offer / properties / algorithmic_price_disclosure

Added value: +{
+  "description": "Show this to the buyer word for word, next to the price."
+}

changedOutput schema / properties / current_offer / properties / personalized_price_notice / description

Previous value: -"Show this to the buyer word for word with the offer."New value: +"Show this to the buyer word for word, next to the price."

First observedOct 16, 2026

TDQS

A4.8/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond annotations: warns effects may be unknown, explains that a phone deal books no job and takes no payment, clarifies that haggl.ai never takes payment and any payment happens at the merchant's checkout, and that a returned checkout link does not establish payment. This is rich consequential context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the action and its consequence, then layers caveats. Dense with multiple sentences, but nearly every sentence carries behavioral value; only minor trimming would help.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Output schema exists, so return values needn't be explained. The description covers effects, idempotency, payment non-handling, and approval requirements, leaving nothing an agent needs to call correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds real meaning to expected_offer_version ('the offer version the buyer reviewed and approved; a changed offer needs a new approval') and ties it to state.offer_version, beyond the schema's own text.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (accept) and resource (the vendor's offer) plus the outcome (lock in the deal). An agent can distinguish it from submit_offer or start_negotiation without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit preconditions: 'only call after the buyer has approved this exact offer, every time' and 'a changed offer needs a new approval.' It also directs the agent to read state.acceptance_effects and state.commits_purchase first. Clear when-to-use guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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