New MCP Server Directory (Agent Tools Index)

data_session_open

Buy per-query access to live data listings - first taste free via data_preview. Listing: New MCP Server Directory (Agent Tools Index) (0.01 USDC/query (max 20 queries/session)). Open a prepaid session, then fund and query.

Input Schema

TableJSON Schema

Name	Required	Description
`listing_id`	No	UUID of the listing. Provide exactly one of listing_slug or listing_id.
`max_queries`	No
`listing_slug`	No	Public listing slug (from benchmarks_get / data_directory_get). Provide exactly one of listing_slug or listing_id.
`open_tx_hash`	No
`buyer_address`	No	Buyer EVM address. Optional: defaults to your own platform wallet when omitted.
`proof_escrow_id`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed13 schema fields changedSep 7, 2026

addedInput schema / description

Added value: +"MCP-only input for ``data_session_open``.\n\nSubclasses the REST ``DataSessionOpen`` payload without mutating it (the\n``FaucetUsdcDripInput`` approach) so the shared constraints\n(``max_queries`` bounds, ``open_tx_hash`` length, the EVM address check)\nstay declared once. Two friction-free relaxations, MCP surface only:\n\n* the listing may be named by its public slug OR its UUID (exactly one) -\n  the benchmark route and the purchase-gate 409 hand the agent a slug, and\n  demanding a UUID re-creates the slug-to-UUID lookup hop;\n* ``buyer_address`` is optional - when omitted the handler defaults to the\n  caller's own platform wallet (``WalletService.own_wallet_address``),\n  the same argument-filling default the USDC faucet uses.\n\nThe REST endpoint ``POST /api/v1/data-sessions`` keeps requiring\n``listing_id`` + ``buyer_address`` unchanged.\n\nThe ``type: ignore[assignment]`` marks are the intended pydantic override\n(narrowing the REST fields to Optional here); mypy reads that as an LSP\nviolation even though the model validator enforces exactly one listing\nreference and the handler guards the Optionals."

addedInput schema / properties / buyer_address / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / buyer_address / default
```
Added value: +null
```

addedInput schema / properties / buyer_address / description

Added value: +"Buyer EVM address. Optional: defaults to your own platform wallet when omitted."

removedInput schema / properties / buyer_address / type
```
Removed value: -"string"
```

addedInput schema / properties / listing_id / anyOf

Added value: +[
+  {
+    "format": "uuid",
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / listing_id / default
```
Added value: +null
```

addedInput schema / properties / listing_id / description

Added value: +"UUID of the listing. Provide exactly one of listing_slug or listing_id."

removedInput schema / properties / listing_id / format
```
Removed value: -"uuid"
```
removedInput schema / properties / listing_id / type
```
Removed value: -"string"
```

addedInput schema / properties / listing_slug

Added value: +{
+  "anyOf": [
+    {
+      "minLength": 1,
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Public listing slug (from benchmarks_get / data_directory_get). Provide exactly one of listing_slug or listing_id.",
+  "title": "Listing Slug"
+}

removedInput schema / required

Removed value: -[
-  "listing_id",
-  "buyer_address"
-]

changedInput schema / title

Previous value: -"DataSessionOpen"New value: +"DataSessionOpenInput"

First observedSep 6, 2026

TDQS

C2.6/5.0

Behavior2/5

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

The description discloses a purchase and prepaid session, but it omits significant behavioral details: it doesn't mention blockchain transaction requirements (open_tx_hash, proof_escrow_id), the need to fund after opening, or that the session has a max query limit (schema allows up to 50, while description mentions 20). It also doesn't address non-idempotency (annotations idempotentHint=false), leaving the agent unaware of potential duplicate session creation.

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

Conciseness3/5

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

The description is short (three sentences) and has a clear sequence, but the inclusion of a specific listing with pricing and limits is extraneous and could confuse agents into thinking the tool is restricted to that listing. It's not a tautology, but it could be more focused.

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

Completeness2/5

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

Given the tool's complexity (financial purchase, blockchain involvement, multiple steps), the description is incomplete. It doesn't explain the overall workflow (open, fund, query), the need for a funded wallet, the output (e.g., session ID), or any error conditions. The schema lacks an output schema, so the description should cover more, but it leaves critical information to the agent's inference.

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

Parameters2/5

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

The description does not reference any of the six parameters, nor does it add meaning beyond the schema's own descriptions. Schema coverage is 50%, and the schema's description block does explain some constraints, but the tool description fails to compensate for undocumented parameters like max_queries, open_tx_hash, and proof_escrow_id. The description's mention of 'max 20 queries/session' contradicts the schema's maximum of 50.

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

Purpose3/5

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

The description states it buys per-query access and opens a prepaid session, which is the core purpose. However, it includes a specific listing reference ('New MCP Server Directory (Agent Tools Index)') that may be misinterpreted as the only supported listing, conflicting with the schema's generic listing_id/listing_slug parameters. It also doesn't clearly distinguish itself from sibling tools like data_session_fund or data_session_query.

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

Usage Guidelines3/5

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

It mentions using data_preview for a free taste, which indicates an alternative for trial purposes, and it outlines a sequence ('Open a prepaid session, then fund and query'). However, it doesn't explicitly state when to use this tool versus data_session_fund or data_session_query, nor does it mention prerequisites like having a wallet or prior setup.

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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