corpusAI Cloud Pricing

Spot price events

spot_events

Read-onlyIdempotent

Paid (0.01 USDC per call). Raw spot price-change events for one instance type. Every price change for the type in the window, with exact timestamp, availability zone and product (OS). Sorted by time. Repeated identical prices are dropped by default (include_repeats=true keeps them). Up to limit rows; when truncated is true, continue with from = next_from.

Input Schema

TableJSON Schema

Name	Required	Description
`az`	No	Restrict to one availability zone / zone id (for example `use1-az1`). Default: all zones.
`to`	No	End of the window (exclusive), ISO 8601 UTC. Default: now.
`from`	No	Start of the window (inclusive), ISO 8601 UTC. Default: 7 days before `to`.
`limit`	No	Maximum rows to return (1 to 10000). Default 5000.
`region`	Yes	Region slug as listed by /catalog (for example `us-east-1` for AWS, `us-central1` for GCP, `us-east` for Azure). Azure slugs map to `eastus`, `westus2`, `westeurope`. Example: us-east-1
`product`	No	Restrict to one product / OS string (for example `Linux/UNIX`, `Spot`, `Linux`). Default: all.
`instance`	Yes	Instance / machine / SKU type name exactly as listed by /instances (for example `c5.large`, `n2-standard-4`, `D2s_v5`). Example: c5.large
`provider`	Yes	Cloud provider. One of `aws`, `gcp`, `azure`.
`include_repeats`	No	Keep events whose price equals the previous event of the same (az, product) series. Default false.

Output Schema

TableJSON Schema

Name	Required	Description
`to`	No
`from`	No
`count`	No
`events`	No
`region`	No
`instance`	No
`provider`	No
`next_from`	No	Pass as `from` to continue when truncated.
`truncated`	No	True when `limit` was hit.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 28, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": true,
+  "properties": {
+    "count": {
+      "type": "number"
+    },
+    "events": {
+      "items": {
+        "additionalProperties": true,
+        "properties": {
+          "az": {
+            "description": "Availability zone or zone id; the region name for GCP.",
+            "type": "string"
+          },
+          "price": {
+            "description": "USD per hour.",
+            "type": "number"
+          },
+          "product": {
+            "description": "Product / OS the price applies to.",
+            "type": "string"
+          },
+          "ts": {
+            "description": "When the price took effect (UTC).",
+            "type": "string"
+          }
+        },
+        "required": [
+          "ts",
+          "az",
+          "product",
+          "price"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "from": {
+      "type": "string"
+    },
+    "instance": {
+      "type": "string"
+    },
+    "next_from": {
+      "description": "Pass as `from` to continue when truncated.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "provider": {
+      "type": "string"
+    },
+    "region": {
+      "type": "string"
+    },
+    "to": {
+      "type": "string"
+    },
+    "truncated": {
+      "description": "True when `limit` was hit.",
+      "type": "boolean"
+    }
+  },
+  "type": "object"
+}

First observedSep 26, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower, yet the description still adds material context: the 0.01 USDC per-call cost, the default dropping of repeated identical prices and how include_repeats overrides it. It does not, however, describe rate limits or auth requirements.

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?

Four tight sentences that lead with the paid cost and resource, then behavior, then pagination. Every sentence carries information; nothing is padded, though the pricing tag is slightly awkwardly front-loaded as an aside.

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?

An output schema exists so return values need not be explained, and the description still covers the cost, the dedup default, and the pagination continuation rule — the details an agent most needs for this event-stream tool. Nothing essential is missing.

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 the baseline is 3, but the description adds meaning beyond the schema by tying include_repeats to the dedup behavior and explaining the pagination contract (limit rows, truncated, continue with from = next_from) referencing output fields not present in the input schema.

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

Purpose4/5

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

The description states a specific verb+resource: it returns raw spot price-change events for one instance type, with per-event timestamp, AZ and product. This implicitly distinguishes it from aggregated siblings like spot_daily, spot_hourly and spot_latest via the word 'raw' and 'every price change', though no sibling is named explicitly.

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?

Usage is implied rather than stated: 'Raw spot price-change events' suggests use when event-level granularity is needed, framing it against aggregated siblings. But there is no explicit when-to-use/when-not or named alternative, and the dedup default is the closest thing to a condition.

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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