Skip to main content
Glama

ASPERN: counterparty checks for agents

Check a service endpoint before connecting

check_service_endpoint
Read-onlyIdempotent

Call this before connecting to a service. Give it the http(s) URL of an MCP or A2A endpoint and it says who declares it, whether our daily probe reached it, what it answered with, and how many of the last readings answered. It keeps three things apart and never merges them: what an identity DECLARES the endpoint offers, what a probe OBSERVED, and the readings behind that. Read drift where present — tools declared but not answering is the signal that an endpoint has changed under the people relying on it. It also answers the three things a buyer wants BEFORE calling a paid endpoint, as separate fields and never folded into one number: price is the seller’s own published amount, asset, network and payee; handshake says whether it answered without credentials, which is the nearest observable thing to “can I try it”; and measured is how many of how many days answered and how slow it was, which is what we read rather than a guarantee anybody made. manifest and changes carry the series: a registration says what an agent offers now, and the readings say what it offered LAST WEEK. Store manifest.hash and compare it next time to detect an endpoint that changed under you. Two things this is NOT: an unreachable endpoint is an availability fact and never evidence of bad faith (weigh latest against history, since one bad day and a dead service look identical in a single reading), and an endpoint we have never probed is outside our reading rather than absent from the world. For a CATALOGUED x402 resource that no agent registered, read unpaidProbe: our own unpaid 402 handshake, which is free for both sides and says whether the endpoint is still there and what it charges now against a catalogue entry that may be months old. Free.

Input Schema

NameRequiredDescriptionDefault
urlYesThe absolute http(s) URL of the service endpoint you are about to connect to.

Output Schema

NameRequiredDescriptionDefault
metaNoHow current this answer is and what it was read from: `freshness` and the ages behind it. Present on every answer from this server, whatever the tool.
saysYesThe reading in one sentence. An endpoint we have never probed says so here: that is our gap, not evidence the service is down.
driftNoDeclared but not observed, and the reverse. Null where either side is unknown — subtracting silence would manufacture a finding.
priceNoThe seller’s OWN published terms for this URL: `amount` in the asset’s own units with `asset` named beside it (a bare number would be read as dollars), `network` as CAIP-2, `payTo`, which catalogues list it, and `cardPriceUsd` where the registration states a price too. Null throughout is UNPRICED, which is not free. Where the card and the catalogue disagree, both are shown — two claims by the same party, and picking one would hide that.
latestNoThe most recent probe: outcome, latency, and what it answered with.
changesNoEvery move we saw in what it offers, oldest first, each with `added`, `removed`, a protocol-version move where there was one, and the two hashes. `at` is the day we SAW the change, not the day it happened: we probe daily and cannot place it more precisely. An empty array where we read a list and it never moved; a tool list we could NOT read is skipped entirely rather than folded in as an empty one, which would invent a “removed everything” out of our own gap.
historyNoUp to fourteen readings. One bad day and a dead service look identical in a single reading.
endpointNoThe URL as we read it back, so a typo is visible before anything is concluded from the answer.
manifestNoWhat the endpoint offers NOW, as something you can bind to: `hash` over the sorted tool names and the declared protocol version and nothing else, with `tools`, `firstSeen`, `lastSeen` and how many readings carried it. Store the hash and compare it on your next call to know whether the offering moved under you. Null where we have never read a tool list here.
measuredNoWhat we measured, which is NOT a guarantee: nothing on these rails publishes one. `serving` of `days`, every outcome by how often, and median and worst latency of the readings that answered. Left as counts with the denominator stated, never a rate and never a grade — 12 of 14 over two weeks means something different from the same fraction over two days, and only the caller can pick the denominator that matters to them.
outcomesNoWhat each outcome word means, so a caller never has to guess.
warningsNoAnything the server wants a caller to know about THIS answer before acting on it. Empty is the normal case and is not a guarantee.
handshakeNoWhether the protocol HANDSHAKE completed without credentials on the latest reading. `open` is the closest thing here to “you can try it” and is NOT a statement that calling its tools is free — a server can answer openly and charge for every call, and we complete a handshake rather than call a tool. `gated` means it asked for something we do not have, which is working as intended. Null where we have no reading.
declaredByNoIdentities that declare this endpoint, and the tools each one claims. Their claim, not our verification.
unpaidProbeNoOUR OWN unpaid x402 handshake with this URL, which is the free availability test for an endpoint no agent registered. x402 requires a server to answer an unpaid request with 402 and its requirements BEFORE doing any work, so the first half of every real client’s handshake costs nothing and proves three things: the host is there, it still speaks x402, and what it asks for NOW. `outcome` is one of quoting, open, refusing, gone, error, unreachable — `open` means it answered 200 unpaid, so it is up and not charging on this path. `quoted.amount` is in the asset’s own smallest unit and is NOT scaled to dollars, because nothing in the requirements document says how many decimals the asset has. Read it beside `price`, which is what the catalogue recorded whenever that entry was written; a price that has moved is a finding neither one shows alone. Null means we have not run this probe here, which is not a finding about the endpoint.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changed
    • addedOutput schema / properties / meta
      Added value: +{
      +  "description": "How current this answer is and what it was read from: `freshness` and the ages behind it. Present on every answer from this server, whatever the tool.",
      +  "type": "object"
      +}
    • addedOutput schema / properties / warnings
      Added value: +{
      +  "description": "Anything the server wants a caller to know about THIS answer before acting on it. Empty is the normal case and is not a guarantee.",
      +  "items": {
      +    "type": "string"
      +  },
      +  "type": "array"
      +}
  2. Changed1 schema field changed
    • addedOutput schema / properties / unpaidProbe
      Added value: +{
      +  "description": "OUR OWN unpaid x402 handshake with this URL, which is the free availability test for an endpoint no agent registered. x402 requires a server to answer an unpaid request with 402 and its requirements BEFORE doing any work, so the first half of every real client’s handshake costs nothing and proves three things: the host is there, it still speaks x402, and what it asks for NOW. `outcome` is one of quoting, open, refusing, gone, error, unreachable — `open` means it answered 200 unpaid, so it is up and not charging on this path. `quoted.amount` is in the asset’s own smallest unit and is NOT scaled to dollars, because nothing in the requirements document says how many decimals the asset has. Read it beside `price`, which is what the catalogue recorded whenever that entry was written; a price that has moved is a finding neither one shows alone. Null means we have not run this probe here, which is not a finding about the endpoint.",
      +  "type": [
      +    "object",
      +    "null"
      +  ]
      +}
  3. Changed2 schema fields changed
    • addedOutput schema / properties / endpoint / description
      Added value: +"The URL as we read it back, so a typo is visible before anything is concluded from the answer."
    • addedOutput schema / properties / says / description
      Added value: +"The reading in one sentence. An endpoint we have never probed says so here: that is our gap, not evidence the service is down."
  4. Changed2 schema fields changed
    • addedOutput schema / properties / changes
      Added value: +{
      +  "description": "Every move we saw in what it offers, oldest first, each with `added`, `removed`, a protocol-version move where there was one, and the two hashes. `at` is the day we SAW the change, not the day it happened: we probe daily and cannot place it more precisely. An empty array where we read a list and it never moved; a tool list we could NOT read is skipped entirely rather than folded in as an empty one, which would invent a “removed everything” out of our own gap.",
      +  "items": {
      +    "type": "object"
      +  },
      +  "type": "array"
      +}
    • addedOutput schema / properties / manifest
      Added value: +{
      +  "description": "What the endpoint offers NOW, as something you can bind to: `hash` over the sorted tool names and the declared protocol version and nothing else, with `tools`, `firstSeen`, `lastSeen` and how many readings carried it. Store the hash and compare it on your next call to know whether the offering moved under you. Null where we have never read a tool list here.",
      +  "type": [
      +    "object",
      +    "null"
      +  ]
      +}
  5. Changed3 schema fields changed
    • addedOutput schema / properties / handshake
      Added value: +{
      +  "description": "Whether the protocol HANDSHAKE completed without credentials on the latest reading. `open` is the closest thing here to “you can try it” and is NOT a statement that calling its tools is free — a server can answer openly and charge for every call, and we complete a handshake rather than call a tool. `gated` means it asked for something we do not have, which is working as intended. Null where we have no reading.",
      +  "enum": [
      +    "open",
      +    "gated",
      +    "no-answer",
      +    null
      +  ],
      +  "type": [
      +    "string",
      +    "null"
      +  ]
      +}
    • addedOutput schema / properties / measured
      Added value: +{
      +  "description": "What we measured, which is NOT a guarantee: nothing on these rails publishes one. `serving` of `days`, every outcome by how often, and median and worst latency of the readings that answered. Left as counts with the denominator stated, never a rate and never a grade — 12 of 14 over two weeks means something different from the same fraction over two days, and only the caller can pick the denominator that matters to them.",
      +  "type": "object"
      +}
    • addedOutput schema / properties / price
      Added value: +{
      +  "description": "The seller’s OWN published terms for this URL: `amount` in the asset’s own units with `asset` named beside it (a bare number would be read as dollars), `network` as CAIP-2, `payTo`, which catalogues list it, and `cardPriceUsd` where the registration states a price too. Null throughout is UNPRICED, which is not free. Where the card and the catalogue disagree, both are shown — two claims by the same party, and picking one would hide that.",
      +  "type": [
      +    "object",
      +    "null"
      +  ]
      +}
  6. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "properties": {
      +    "declaredBy": {
      +      "description": "Identities that declare this endpoint, and the tools each one claims. Their claim, not our verification.",
      +      "items": {
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "drift": {
      +      "description": "Declared but not observed, and the reverse. Null where either side is unknown — subtracting silence would manufacture a finding.",
      +      "type": [
      +        "object",
      +        "null"
      +      ]
      +    },
      +    "endpoint": {
      +      "type": "string"
      +    },
      +    "history": {
      +      "description": "Up to fourteen readings. One bad day and a dead service look identical in a single reading.",
      +      "items": {
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "latest": {
      +      "description": "The most recent probe: outcome, latency, and what it answered with.",
      +      "type": [
      +        "object",
      +        "null"
      +      ]
      +    },
      +    "outcomes": {
      +      "description": "What each outcome word means, so a caller never has to guess.",
      +      "type": "object"
      +    },
      +    "says": {
      +      "type": "string"
      +    }
      +  },
      +  "required": [
      +    "says"
      +  ],
      +  "type": "object"
      +}
  7. Added

TDQS

A3.6/5.0
Behavior4/5

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

Annotations already declare the safe, idempotent, open-world read profile, so safety isn't the burden here. The description adds genuinely non-structured traits: the call is free, it distinguishes declared vs observed vs reading layers, and it warns against over-reading a single `latest` value. Much of the remaining prose is output interpretation that the output schema likely already carries.

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

Conciseness2/5

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

The opening sentence is well front-loaded, but the body runs several hundred words for a one-parameter read tool, with repeated emphases ("never merges them," "never folded into one number," "separate fields") and field-by-field exposition that belongs in the output schema. Several sentences do not earn their place in a tool-selection document.

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

Completeness4/5

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, yet the description still covers semantics, caveats, and the drift/freshness interpretation an agent needs before calling. Nothing essential is missing; the issue is excess rather than incompleteness.

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

Parameters3/5

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

There is exactly one parameter with 100% schema description coverage, so the baseline is 3. The description restates that it takes the http(s) URL of the endpoint but adds no format, constraint, or edge-case detail beyond the schema's own wording.

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 and resource: give it an http(s) URL of an MCP or A2A endpoint and it reports who declares it, whether the probe reached it, what it answered, and how many readings responded. That is a real, distinguishable purpose. It never names a sibling tool, so it lacks the explicit differentiation a 5 requires.

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

Usage Guidelines4/5

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

"Call this before connecting to a service" gives a clear trigger condition, and it adds exclusion-style guidance: unreachable is an availability fact, not bad faith, and unprobed endpoints are outside the reading. It also routes one case (catalogued x402 resources with no registered agent) to reading `unpaidProbe`. No alternative tool is ever named, so it stops short of a 5.

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

Try in Browser

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources