healthFree. Feed health: feed_lag_s (seconds behind the newest event), is_stale, last Solana slot, chain_lag_s and slots_behind (how far the tape is behind the chain, estimated from slots against the Solana RPC's processed tip). Use it before trusting a card's freshness.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| ok | No | ||
| data | No | ||
| meta | No | ||
| coverage | No |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "coverage": {
+ "type": "string"
+ },
+ "data": {
+ "type": [
+ "object",
+ "null"
+ ]
+ },
+ "meta": {
+ "type": "object"
+ },
+ "ok": {
+ "type": "boolean"
+ }
+ },
+ "type": "object"
+}Output schema / (root)Previous value: -{
- "anyOf": [
- {
- "properties": {
- "coverage": {
- "enum": [
- "full",
- "thin"
- ]
- },
- "data": {
- "properties": {
- "feed_lag_s": {
- "type": [
- "number",
- "null"
- ]
- },
- "is_stale": {
- "type": "boolean"
- },
- "last_slot": {
- "type": [
- "integer",
- "null"
- ]
- }
- },
- "required": [
- "feed_lag_s",
- "is_stale"
- ],
- "type": "object"
- },
- "meta": {
- "type": "object"
- },
- "ok": {
- "const": true
- }
- },
- "required": [
- "ok",
- "schema_version",
- "generated_at",
- "t",
- "coverage",
- "data",
- "meta"
- ],
- "type": "object"
- },
- {
- "properties": {
- "error": {
- "type": "string"
- },
- "ok": {
- "const": false
- }
- },
- "required": [
- "ok",
- "error"
- ],
- "type": "object"
- }
- ],
- "type": "object"
-}New value: +nullInput schema / titleRemoved value: -"healthArguments"Output schema / anyOfPrevious value: -[
- {
- "properties": {
- "coverage": {
- "enum": [
- "full",
- "thin"
- ]
- },
- "data": {
- "properties": {
- "feed_lag_s": {
- "type": [
- "number",
- "null"
- ]
- },
- "is_stale": {
- "type": "boolean"
- },
- "last_slot": {
- "type": [
- "integer",
- "null"
- ]
- }
- },
- "required": [
- "feed_lag_s",
- "is_stale"
- ],
- "type": "object"
- },
- "generated_at": {
- "type": "string"
- },
- "meta": {
- "properties": {
- "feed_lag_s": {
- "type": [
- "number",
- "null"
- ]
- },
- "is_stale": {
- "type": "boolean"
- }
- },
- "type": "object"
- },
- "ok": {
- "const": true
- },
- "schema_version": {
- "type": "string"
- },
- "t": {
- "type": "number"
- }
- },
- "required": [
- "ok",
- "schema_version",
- "generated_at",
- "t",
- "coverage",
- "data",
- "meta"
- ],
- "title": "FeedHealth",
- "type": "object"
- },
- {
- "description": "isError: the x402 v2 payment requirements. Pay one accepts entry and call again with _meta['x402/payment']. error says why when a payment was sent and rejected; a failed settlement adds x402/payment-response. Nothing is charged.",
- "properties": {
- "accepts": {
- "items": {
- "properties": {
- "amount": {
- "type": "string"
- },
- "asset": {
- "type": "string"
- },
- "extra": {
- "type": "object"
- },
- "maxTimeoutSeconds": {
- "type": "integer"
- },
- "network": {
- "type": "string"
- },
- "payTo": {
- "type": "string"
- },
- "scheme": {
- "type": "string"
- }
- },
- "required": [
- "scheme",
- "network",
- "amount",
- "asset",
- "payTo"
- ],
- "type": "object"
- },
- "minItems": 1,
- "type": "array"
- },
- "error": {
- "type": "string"
- },
- "extensions": {
- "type": "object"
- },
- "resource": {
- "properties": {
- "description": {
- "type": "string"
- },
- "mimeType": {
- "type": "string"
- },
- "url": {
- "type": "string"
- }
- },
- "required": [
- "url"
- ],
- "type": "object"
- },
- "x402/payment-response": {
- "properties": {
- "errorReason": {
- "type": "string"
- },
- "network": {
- "type": "string"
- },
- "success": {
- "type": "boolean"
- },
- "transaction": {
- "type": "string"
- }
- },
- "required": [
- "success"
- ],
- "type": "object"
- },
- "x402Version": {
- "const": 2
- }
- },
- "required": [
- "x402Version",
- "resource",
- "accepts"
- ],
- "title": "PaymentRequired",
- "type": "object"
- },
- {
- "description": "isError: a refusal answered without charging (invalid or uncovered arguments, stale feed, nothing new since the cursor, a payment that cannot be matched to this request). error is a stable code; live_examples name mints covered now.",
- "properties": {
- "address": {
- "type": "string"
- },
- "avoid_skipped": {
- "type": "integer"
- },
- "case_mangled_mints": {
- "items": {
- "type": "string"
- },
- "type": "array"
- },
- "charged": {
- "type": [
- "boolean",
- "null"
- ]
- },
- "curve": {
- "type": "string"
- },
- "error": {
- "type": "string"
- },
- "feed_lag_s": {
- "type": [
- "number",
- "null"
- ]
- },
- "free_check": {
- "type": "string"
- },
- "got": {
- "type": [
- "string",
- "integer"
- ]
- },
- "hint": {
- "type": "string"
- },
- "invalid": {
- "type": "object"
- },
- "live_examples": {
- "items": {
- "type": "string"
- },
- "type": "array"
- },
- "max_feed_lag_s": {
- "type": "number"
- },
- "max_mints": {
- "type": "integer"
- },
- "max_table_lag_s": {
- "type": "number"
- },
- "message": {
- "type": "string"
- },
- "mint": {
- "type": "string"
- },
- "missing": {
- "items": {
- "type": "string"
- },
- "type": "array"
- },
- "newest_cursor": {
- "type": "string"
- },
- "ok": {
- "const": false
- },
- "payment_status": {
- "type": "string"
- },
- "scanned": {
- "type": "integer"
- },
- "schema": {
- "type": "object"
- },
- "since": {
- "type": [
- "string",
- "null"
- ]
- },
- "table_lag_s": {
- "type": [
- "number",
- "null"
- ]
- },
- "tool": {
- "type": "string"
- },
- "unavailable_mints": {
- "items": {
- "type": "string"
- },
- "type": "array"
- },
- "unverified_event": {
- "type": [
- "object",
- "null"
- ]
- },
- "window_s": {
- "type": "number"
- }
- },
- "required": [
- "ok",
- "error"
- ],
- "title": "Refusal",
- "type": "object"
- }
-]New value: +[
+ {
+ "properties": {
+ "coverage": {
+ "enum": [
+ "full",
+ "thin"
+ ]
+ },
+ "data": {
+ "properties": {
+ "feed_lag_s": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "is_stale": {
+ "type": "boolean"
+ },
+ "last_slot": {
+ "type": [
+ "integer",
+ "null"
+ ]
+ }
+ },
+ "required": [
+ "feed_lag_s",
+ "is_stale"
+ ],
+ "type": "object"
+ },
+ "meta": {
+ "type": "object"
+ },
+ "ok": {
+ "const": true
+ }
+ },
+ "required": [
+ "ok",
+ "schema_version",
+ "generated_at",
+ "t",
+ "coverage",
+ "data",
+ "meta"
+ ],
+ "type": "object"
+ },
+ {
+ "properties": {
+ "error": {
+ "type": "string"
+ },
+ "ok": {
+ "const": false
+ }
+ },
+ "required": [
+ "ok",
+ "error"
+ ],
+ "type": "object"
+ }
+]Output schema / descriptionRemoved value: -"One of three shapes. Success (isError false): the JSON envelope {ok, schema_version, generated_at, t, coverage, data, meta}. isError true: the x402 PaymentRequired {x402Version 2, resource, accepts[, error]} (pay and call again) or a refusal {ok: false, error, message, charged: false}; neither is charged."Output schema / (root)Previous value: -nullNew value: +{
+ "anyOf": [
+ {
+ "properties": {
+ "coverage": {
+ "enum": [
+ "full",
+ "thin"
+ ]
+ },
+ "data": {
+ "properties": {
+ "feed_lag_s": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "is_stale": {
+ "type": "boolean"
+ },
+ "last_slot": {
+ "type": [
+ "integer",
+ "null"
+ ]
+ }
+ },
+ "required": [
+ "feed_lag_s",
+ "is_stale"
+ ],
+ "type": "object"
+ },
+ "generated_at": {
+ "type": "string"
+ },
+ "meta": {
+ "properties": {
+ "feed_lag_s": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "is_stale": {
+ "type": "boolean"
+ }
+ },
+ "type": "object"
+ },
+ "ok": {
+ "const": true
+ },
+ "schema_version": {
+ "type": "string"
+ },
+ "t": {
+ "type": "number"
+ }
+ },
+ "required": [
+ "ok",
+ "schema_version",
+ "generated_at",
+ "t",
+ "coverage",
+ "data",
+ "meta"
+ ],
+ "title": "FeedHealth",
+ "type": "object"
+ },
+ {
+ "description": "isError: the x402 v2 payment requirements. Pay one accepts entry and call again with _meta['x402/payment']. error says why when a payment was sent and rejected; a failed settlement adds x402/payment-response. Nothing is charged.",
+ "properties": {
+ "accepts": {
+ "items": {
+ "properties": {
+ "amount": {
+ "type": "string"
+ },
+ "asset": {
+ "type": "string"
+ },
+ "extra": {
+ "type": "object"
+ },
+ "maxTimeoutSeconds": {
+ "type": "integer"
+ },
+ "network": {
+ "type": "string"
+ },
+ "payTo": {
+ "type": "string"
+ },
+ "scheme": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "scheme",
+ "network",
+ "amount",
+ "asset",
+ "payTo"
+ ],
+ "type": "object"
+ },
+ "minItems": 1,
+ "type": "array"
+ },
+ "error": {
+ "type": "string"
+ },
+ "extensions": {
+ "type": "object"
+ },
+ "resource": {
+ "properties": {
+ "description": {
+ "type": "string"
+ },
+ "mimeType": {
+ "type": "string"
+ },
+ "url": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "url"
+ ],
+ "type": "object"
+ },
+ "x402/payment-response": {
+ "properties": {
+ "errorReason": {
+ "type": "string"
+ },
+ "network": {
+ "type": "string"
+ },
+ "success": {
+ "type": "boolean"
+ },
+ "transaction": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "success"
+ ],
+ "type": "object"
+ },
+ "x402Version": {
+ "const": 2
+ }
+ },
+ "required": [
+ "x402Version",
+ "resource",
+ "accepts"
+ ],
+ "title": "PaymentRequired",
+ "type": "object"
+ },
+ {
+ "description": "isError: a refusal answered without charging (invalid or uncovered arguments, stale feed, nothing new since the cursor, a payment that cannot be matched to this request). error is a stable code; live_examples name mints covered now.",
+ "properties": {
+ "address": {
+ "type": "string"
+ },
+ "avoid_skipped": {
+ "type": "integer"
+ },
+ "case_mangled_mints": {
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "charged": {
+ "type": [
+ "boolean",
+ "null"
+ ]
+ },
+ "curve": {
+ "type": "string"
+ },
+ "error": {
+ "type": "string"
+ },
+ "feed_lag_s": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "free_check": {
+ "type": "string"
+ },
+ "got": {
+ "type": [
+ "string",
+ "integer"
+ ]
+ },
+ "hint": {
+ "type": "string"
+ },
+ "invalid": {
+ "type": "object"
+ },
+ "live_examples": {
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "max_feed_lag_s": {
+ "type": "number"
+ },
+ "max_mints": {
+ "type": "integer"
+ },
+ "max_table_lag_s": {
+ "type": "number"
+ },
+ "message": {
+ "type": "string"
+ },
+ "mint": {
+ "type": "string"
+ },
+ "missing": {
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "newest_cursor": {
+ "type": "string"
+ },
+ "ok": {
+ "const": false
+ },
+ "payment_status": {
+ "type": "string"
+ },
+ "scanned": {
+ "type": "integer"
+ },
+ "schema": {
+ "type": "object"
+ },
+ "since": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "table_lag_s": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "tool": {
+ "type": "string"
+ },
+ "unavailable_mints": {
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "unverified_event": {
+ "type": [
+ "object",
+ "null"
+ ]
+ },
+ "window_s": {
+ "type": "number"
+ }
+ },
+ "required": [
+ "ok",
+ "error"
+ ],
+ "title": "Refusal",
+ "type": "object"
+ }
+ ],
+ "description": "One of three shapes. Success (isError false): the JSON envelope {ok, schema_version, generated_at, t, coverage, data, meta}. isError true: the x402 PaymentRequired {x402Version 2, resource, accepts[, error]} (pay and call again) or a refusal {ok: false, error, message, charged: false}; neither is charged.",
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds the semantics of chain_lag_s/slots_behind (estimated from slots against the Solana RPC processed tip) and flags the tool as free, but an output schema already exists, so return fields are partly redundant.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, front-loaded with "Free. Feed health:" and then the field roster plus the usage cue. The parenthetical explanations are dense but each earns its place by defining non-obvious lag metrics.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Zero parameters, rich annotations, and a published output schema mean the description only needs to state what the tool is and when to reach for it, both of which it does. Nothing needed to invoke it correctly is missing.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Names a specific resource (feed health) and enumerates the concrete signals returned: feed_lag_s, is_stale, last Solana slot, chain_lag_s, slots_behind. The purpose is unambiguous, though it never explicitly contrasts itself with the many risk/card siblings it warns about.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
"Use it before trusting a card's freshness" gives a clear trigger condition tied to sibling card tools. It stops short of naming an alternative or stating when not to call it, so it is clear context without exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.