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MCP Client Compatibility Probe

by kascada

MCP-Client-Kompatibilitäts-Sonde

Kleiner diagnostischer MCP-Server zur Prüfung, welche MCP-Clients tatsächlich unterstützen.

Der Server ist bewusst ohne Abhängigkeiten gehalten und in eine transportneutrale Kernlogik plus einen lokalen stdio-Adapter aufgeteilt. Ein zukünftiger HTTP-Adapter kann probe-core.mjs für ChatGPT Web, OpenAI-API oder Remote-MCP-Tests wiederverwenden.

Der vorgesehene Ablauf ist KI-gestützt: Richten Sie den Assistenten/Client, den Sie testen möchten, auf dieses Repository aus und lassen Sie ihn die Sonde ausführen, die Ablaufspur prüfen, eine Ergebnisdatei erstellen und einen Commit vorbereiten. In der Praxis ist das ein einziger Prompt.

Die aktuelle informelle Client-Unterstützungsübersicht befindet sich in CLIENT-MATRIX.md. Detaillierte Testentwürfe und Ergebnisvorlagen befinden sich in TESTPLAN.md.

Schnellstart für Tester

Option A: Ein Prompt

Starten Sie den Assistenten oder Client, den Sie testen möchten, in einem Verzeichnis, in das er schreiben darf, und geben Sie ihm Folgendes:

Clone https://github.com/kascada/mcp-client-compat-probe.git, then read PROMPT.md from that clone and follow the prompt inside it. You are the client under test.

Das ist die gesamte Einrichtung. Von dort aus klont der Assistent das Repository, führt den Smoke-Test aus, registriert die Sonde als lokalen MCP-Server, führt die Sonden-Interaktionen aus, prüft die Ablaufspur und schreibt die Ergebnisdatei. Er kommt nur zu Ihnen zurück, wenn er etwas nicht selbst tun kann: den Client neu starten, damit er die MCP-Konfiguration übernimmt, etwas aufrufen, das der Client nur als Benutzeraktion anbietet, und den Push oder Pull-Request genehmigen.

Dies setzt einen Client voraus, der Shell-Befehle ausführen und lokale Dateien lesen kann, wie Claude Code, Codex CLI, OpenCode oder Cursor. Wenn Ihr Client das nicht kann, verwenden Sie Option B.

Option B: Schritt für Schritt

Der gleiche Test, ausführlich beschrieben. Verwenden Sie dies, wenn Ihr Client nicht selbst klonen kann, oder wenn Sie sehen möchten, was Option A tun wird, bevor Sie es ausführen.

  1. Klonen Sie dieses Repository.

    git clone https://github.com/kascada/mcp-client-compat-probe.git
    cd mcp-client-compat-probe

    HTTPS wird für die meisten Tester empfohlen, da es ohne konfigurierten SSH-Schlüssel funktioniert. Wenn Sie GitHub bereits über SSH verwenden, ist dies gleichwertig:

    git clone git@github.com:kascada/mcp-client-compat-probe.git
    cd mcp-client-compat-probe
  2. Öffnen Sie das geklonte Verzeichnis in dem MCP-fähigen Assistenten/Client, den Sie testen möchten.

  3. Bitten Sie den Assistenten, PROMPT.md auszuführen, zum Beispiel: Run PROMPT.md. Wenn der Assistent keine lokalen Dateien lesen kann, fügen Sie stattdessen den vollständigen Inhalt von PROMPT.md ein.

  4. Befolgen Sie nur die expliziten Aufforderungen zum Neustart des Clients, zur Bestätigung der MCP-Einrichtung und zur Genehmigung von Push/PR.

Der Assistent sollte den Rest übernehmen:

  • npm run smoke ausführen

  • bei der Konfiguration des lokalen stdio-MCP-Servers helfen, falls erforderlich

  • die Sonden-Interaktionen ausführen

  • die Ablaufspurdatei prüfen

  • results/<client>-<username>-<date>.md schreiben

  • nur diese Ergebnisdatei stagen und committen

Committen Sie standardmäßig keine vollständigen Ablaufspurdateien. Ergebnisdateien sollten nur kleine geschwärzte Auszüge enthalten.

Related MCP server: jakegaylor-com-mcp-server

Ein Ergebnis beitragen

Dieses Repository ist öffentlich, was bedeutet, dass jeder es lesen und klonen kann, aber nicht darauf pushen kann. Das Klonen erstellt keinen Fork und gewährt keinen Schreibzugriff. Daher erfolgt das Beitragen eines Ergebnisses über einen Pull-Request von Ihrem eigenen Fork. Der Assistent kann dies für Sie erledigen; das manuelle Äquivalent ist:

gh repo fork --remote                                   # your own fork, no permissions needed here
git switch -c probe-result-<client>-<username>
git add results/<client>-<username>-<date>.md           # only the result file
git commit -m "Add <client> probe result <username> <date>"
git push -u origin probe-result-<client>-<username>     # pushes to your fork
gh pr create --repo kascada/mcp-client-compat-probe

Verwenden Sie Ihren GitHub-Benutzernamen als <username>, damit das Ergebnis in der gemeinsamen Sammlung zugeordnet werden kann.

Wenn Sie keinen Pull-Request öffnen können oder möchten, sind beide dieser Optionen ebenfalls in Ordnung:

  • Öffnen Sie ein Issue und hängen Sie die Ergebnisdatei an.

  • Senden Sie die Ergebnisdatei direkt an den Repository-Autor, zusammen mit der Client-Version, dem Betriebssystem und Ihrer MCP-Konfiguration ohne Geheimnisse.

Dateien

mcp-probe/
  README.md              # quickstart and feature overview
  CLIENT-MATRIX.md       # informal client support matrix
  PROMPT.md              # assistant prompt for running and recording tests
  TESTPLAN.md            # repeatable client test plan
  probe-core.mjs          # JSON-RPC handlers and probe tools
  stdio-server.mjs        # local stdio transport
  opencode.json           # isolated OpenCode test config
  package.json            # npm scripts, no dependencies
  results/                # contributed client observations
  scripts/smoke-stdio.mjs # direct stdio smoke test

Sondenabdeckung

Implementierte MCP-Methoden:

  • server/discover

  • Legacy-initialize-Fallback-Antwort

  • tools/list

  • tools/call

  • resources/list

  • resources/read

  • resources/templates/list

  • prompts/list

  • prompts/get

  • Stub subscriptions/listen

Werkzeuge:

  • echo_meta: gibt empfangene Argumente, _meta, Client-Fähigkeiten und Transportbeobachtungen zurück.

  • structured_result: gibt Text plus structuredContent zurück, das einem outputSchema entspricht.

  • create_handle: erstellt einen expliziten Zustands-Handle.

  • use_handle: verwendet einen Handle aus create_handle.

  • needs_form_input: gibt resultType: "input_required" zurück, bis mit inputResponses erneut versucht wird.

  • tool_error: gibt einen Werkzeugausführungsfehler über isError: true zurück.

  • resource_link_result: gibt ein resource_link-Inhaltselement zurück.

  • search: ChatGPT-kompatibler Such-Stub.

  • fetch: ChatGPT-kompatibler Fetch-Stub.

Smoke-Test

Führen Sie von diesem Verzeichnis aus aus:

npm run smoke

Oder ohne npm:

node scripts/smoke-stdio.mjs

Der Smoke-Test schreibt seine Ablaufspur nach:

/tmp/mcp-probe-smoke.ndjson

Ablaufprotokoll

Der Server schreibt nie Diagnose an stdout, weil stdout nur MCP-JSON-RPC-Nachrichten enthalten muss. Diagnosen gehen an stderr und in die Ablaufspurdatei.

Standard-Ablaufspfad:

/tmp/mcp-probe.ndjson

OpenCode-Ablaufspfad aus opencode.json:

/tmp/mcp-probe-opencode.ndjson

Jede Zeile ist JSON mit:

  • ts: Zeitstempel

  • pid: Server-Prozess-ID

  • direction: in oder out

  • payload: JSON-RPC-Nutzlast

Test mit OpenCode

Dieses Verzeichnis enthält eine isolierte opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "probe": {
      "type": "local",
      "command": ["node", "stdio-server.mjs"],
      "cwd": ".",
      "enabled": true,
      "timeout": 10000,
      "environment": {
        "MCP_PROBE_TRACE": "/tmp/mcp-probe-opencode.ndjson"
      }
    }
  }
}

Starten Sie OpenCode aus diesem Verzeichnis, damit es die lokale Konfiguration lädt:

opencode

Dann fragen Sie:

Nutze das probe echo_meta Tool und zeige mir, welche MCP-Metadaten du gesendet hast.

Weitere nützliche Prompts:

Nutze probe structured_result mit label opencode.
Erzeuge mit probe create_handle ein Handle fuer confluence und nutze es danach mit probe use_handle fuer die Query release notes.
Teste probe needs_form_input fuer topic OpenCode Elicitation.
Nutze probe search fuer query probe und danach probe fetch fuer das erste Ergebnis.

Interpretieren Sie die Ablaufspur:

  • server/discover vorhanden: Die moderne MCP-Erkundungssonde wird verwendet.

  • initialize vorhanden: Der Legacy-Handshake-Pfad wird verwendet.

  • _meta.io.modelcontextprotocol/protocolVersion vorhanden: Die Protokollversion pro Anfrage wird gesendet.

  • _meta.io.modelcontextprotocol/clientCapabilities.elicitation vorhanden: Der Client deklariert Unterstützung für Elicitation.

  • resources/list oder prompts/list vorhanden: Der Client fragt aktiv Nicht-Werkzeug-Primitives ab.

  • Wiederholung nach input_required: MRTR/Elicitation-Ablauf wird behandelt.

OpenCode liest die Konfiguration beim Start. Starten Sie OpenCode neu, nachdem Sie opencode.json oder Serverdateien geändert haben.

Test mit Codex CLI oder ChatGPT Desktop

Der gleiche lokale stdio-Server kann von Codex CLI, der ChatGPT-Desktop-App und der Codex-IDE-Erweiterung verwendet werden, da sie lokale MCP-Server unterstützen.

Beispiel für die Codex-CLI-Registrierung aus diesem Verzeichnis:

codex mcp add probe --env MCP_PROBE_TRACE=/tmp/mcp-probe-codex.ndjson -- node stdio-server.mjs

Verwenden Sie dann /mcp in Codex, um aktive Server zu prüfen und die gleichen Sonden-Werkzeuge wie oben anzufordern.

Für die ChatGPT-Desktop-App fügen Sie einen neuen MCP-Server in den Einstellungen hinzu mit:

  • Name: probe

  • Typ: STDIO

  • Befehl: node

  • Argumente: absoluter Pfad zu stdio-server.mjs

  • Umgebung: MCP_PROBE_TRACE=/tmp/mcp-probe-chatgpt-desktop.ndjson

ChatGPT Web und OpenAI-API-Pfad

ChatGPT Web kann keinen lokalen stdio-Server direkt starten oder die lokale Codex/OpenCode-Konfiguration lesen. Für ChatGPT-Web- oder OpenAI-API-Tests fügen Sie später einen entfernten HTTP-Adapter hinzu.

Das aktuelle Design hält diesen Pfad offen:

  • probe-core.mjs hat kein stdio-spezifisches Verhalten.

  • stdio-server.mjs passt nur zeilengetrenntes JSON-RPC an handleJsonRpc an.

  • Ein zukünftiger http-server.mjs kann dieselbe handleJsonRpc aufrufen und HTTP-Header im Transportobjekt übergeben.

  • Die vorhandenen search- und fetch-Werkzeuge folgen bereits der einfachen ChatGPT-kompatiblen Form mit structuredContent und URL-gestützten Ergebnissen.

HTTP-spezifische Prüfungen, die später hinzugefügt werden:

  • MCP-Protocol-Version, Mcp-Method, Mcp-Name

  • statische/Bearer-Header

  • OAuth-Verhalten

  • x-mcp-header aus Werkzeugparametern

  • Streamable-HTTP-Antwortverhalten

Available Tools

9 tools
create_handleCreate HandleA

Creates an explicit short-lived probe handle to test stateless multi-call tool design.

ParametersJSON Schema
NameRequiredDescriptionDefault
targetYesTarget system or scenario for the handle.

Output Schema

ParametersJSON Schema
NameRequiredDescription
handleYes
targetYes
expiresInSecondsYes

TDQS

A3.5/5.0
Behavior2/5

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

With no annotations, the description carries the full burden of behavioral disclosure. It mentions the handle is 'short-lived' and 'explicit,' but does not explain what the handle is for, what it returns, any side effects, or lifecycle details. For a creation tool, this is insufficient.

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

Conciseness5/5

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

The description is a single sentence, front-loaded with the action, and contains no unnecessary words. It is appropriately concise.

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

Completeness3/5

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

The tool is simple (1 parameter) and has an output schema, so the description does not need to explain return values. However, it lacks context about how the handle is used, its lifecycle, and its relationship to sibling tools like use_handle. This incomplete context could confuse agents.

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?

The input schema has 100% description coverage for the 'target' parameter, so the baseline is 3. The tool description adds no additional parameter-level context beyond restating the purpose.

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?

The description clearly states the verb 'creates' and the resource 'explicit short-lived probe handle,' and it adds the specific purpose 'to test stateless multi-call tool design.' This distinguishes it from sibling tools like use_handle, which presumably consumes the handle.

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?

The description implies usage for testing stateless multi-call tool design but does not explicitly state when to use this tool versus alternatives like use_handle. No exclusions or when-not-to-use guidance is provided.

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

echo_metaEcho MetadataA

Returns the received arguments and MCP request metadata. Use this first to inspect protocolVersion, clientInfo, and clientCapabilities.

ParametersJSON Schema
NameRequiredDescriptionDefault
messageNoAny message to echo back.

Output Schema

ParametersJSON Schema
NameRequiredDescription
metaYes
observedYes
argumentsYes

TDQS

A4.3/5.0
Behavior4/5

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

With no annotations provided, the description carries the full burden. It transparently states that the tool returns the received arguments and MCP metadata, and specifically calls out the metadata fields. This is a read-only behavior implied by 'Returns,' and it discloses what the agent can expect without needing to infer hidden side effects.

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

Conciseness5/5

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

The description is exactly two sentences. The first sentence states the core function, and the second provides usage guidance. Every word earns its place, with no filler or repetition. It is front-loaded with the primary purpose and immediately actionable.

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?

This is a simple tool with one optional parameter and an output schema present. The description fully covers its purpose and usage context. Since the output schema exists, the description does not need to explain return values. For the tool's complexity, the description is complete and well-rounded.

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?

The input schema fully documents the only parameter 'message' with a description ('Any message to echo back'), so schema coverage is 100%. The description does not add any additional parameter-specific meaning beyond what the schema provides, but it does mention 'received arguments' which encompasses the parameter. This meets the baseline of 3.

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?

The description clearly states the tool 'Returns the received arguments and MCP request metadata,' which is a specific verb+resource combination. It distinguishes itself from siblings by explicitly mentioning metadata fields (protocolVersion, clientInfo, clientCapabilities) and the directive to 'Use this first,' making its diagnostic role clear.

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?

The description gives explicit usage context: 'Use this first to inspect protocolVersion, clientInfo, and clientCapabilities.' This tells the agent when to invoke the tool, though it does not explicitly name alternatives or exclusions. The clear 'use this first' directive provides adequate guidance.

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

fetchFetch Probe DocumentA
Read-only

ChatGPT-compatible read-only fetch stub. Retrieves full text for an ID returned by search.

ParametersJSON Schema
NameRequiredDescriptionDefault
idYesDocument ID returned by search.

Output Schema

ParametersJSON Schema
NameRequiredDescription
idYes
urlYes
textYes
titleYes
metadataNo

TDQS

A4.3/5.0
Behavior4/5

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

Beyond the readOnlyHint annotation, the description adds that this is a 'ChatGPT-compatible' and a 'stub,' suggesting a simulated or compatibility-oriented behavior, and that it returns 'full text' for the ID. This provides useful context not present in annotations, with no contradictions.

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

Conciseness5/5

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

The description is two short sentences with no filler. The first provides contextual framing ('stub'), the second the core functionality. Every word contributes meaning.

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?

For a simple one-parameter fetch operation with an output schema and clear read-only annotation, the description sufficiently covers purpose, input requirement, and relationship to search. The 'stub' characterization adds a behavioral hint without needing further detail.

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?

The schema already provides 100% parameter coverage with 'Document ID returned by search.' The tool description echoes the same requirement without adding new semantic details, so it stays at the baseline for high schema coverage.

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?

The description clearly states 'Retrieves full text for an ID returned by search,' specifying the verb (retrieves), resource (full text), and the relationship to the search tool. This distinguishes it from siblings like search (which finds IDs) and handle tools.

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?

The description explicitly ties usage to search by requiring an ID returned by search, implying the correct invocation sequence. It does not explicitly name alternatives or exclusion conditions, so it doesn't reach a 5.

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

needs_form_inputNeeds Form InputA

Returns resultType input_required until the client retries with inputResponses. This tests MRTR and elicitation form mode.

ParametersJSON Schema
NameRequiredDescriptionDefault
topicYesTopic for the requested follow-up input.

TDQS

A4.2/5.0
Behavior4/5

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

With no annotations, the description carries the full burden. It discloses the key behavioral trait: the tool repeatedly returns input_required until the client sends inputResponses. However, it doesn't specify what happens after the retry or any side effects, but for a simple test tool this is adequate.

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

Conciseness5/5

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

Two sentences, front-loaded with the return behavior and testing purpose. No wasted words.

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?

For a simple tool with one parameter and no output schema, the description covers the core behavior and purpose. It might benefit from stating the expected response after inputResponses, but the description is sufficient for an agent to understand invocation context.

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?

Schema coverage is 100% with a clear description of 'topic'. The main description doesn't add significant new meaning beyond the schema; it reinforces the context of follow-up input but doesn't explain format or constraints. Baseline 3 applies given high schema coverage.

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?

The description explicitly states the tool's behavior: it returns resultType input_required until retried with inputResponses. It also states its testing purpose (MRTR and elicitation form mode), clearly distinguishing it from siblings like echo_meta or structured_result.

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?

The description identifies a clear use case: testing MRTR and elicitation form mode. It doesn't explicitly mention when not to use it or alternatives, but the testing context is specific enough for an agent to select it appropriately.

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

structured_resultStructured ResultB

Returns both text content and structuredContent conforming to outputSchema.

ParametersJSON Schema
NameRequiredDescriptionDefault
labelNoOptional label for the generated result.

Output Schema

ParametersJSON Schema
NameRequiredDescription
labelYes
answerYes
nestedYes

TDQS

B3.4/5.0
Behavior3/5

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

No annotations are provided, so the description must carry the full burden of disclosing behavior. It does state the core return behavior (both text and structuredContent), which is useful, but it does not address the role of the label parameter, edge cases, or any limitations. This is minimal but not misleading.

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

Conciseness5/5

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

The description is one sentence that front-loads the primary action and includes no filler or redundant information. Every word contributes to understanding the tool's function, making it highly concise and well-structured.

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?

The tool is simple: one optional parameter, no required fields, and an output schema. The description states the core return behavior, and the output schema presumably covers the structure of structuredContent. However, it does not mention the intended use case or how the label parameter influences the result, leaving a small but noticeable gap. Given the simplicity, it is mostly complete.

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?

The input schema has 100% coverage for the single optional 'label' parameter, described as 'Optional label for the generated result.' The description adds no further semantic detail about how the label affects the output, so it remains at the baseline for high schema coverage without adding extra value.

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 the tool's primary function: returning both text content and structuredContent conforming to outputSchema. This clearly identifies what the tool does, though it does not explicitly differentiate it from sibling tools like resource_link_result. The verb 'Returns' and the specific resource make the purpose clear.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool versus alternatives. The description only states what it does, without mentioning any context, prerequisites, or exclusions. Sibling tools are listed but not referenced, so the description fails to help the agent decide when to invoke this tool.

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

tool_errorTool ErrorA

Always returns a tool execution error via isError true, not a JSON-RPC protocol error.

ParametersJSON Schema
NameRequiredDescriptionDefault

No parameters

TDQS

A4.1/5.0
Behavior4/5

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

With no annotations, the description carries the full disclosure responsibility. It clearly states the tool always errors with isError true and clarifies that it is not a protocol-level error, providing useful context. It does not detail the error message content, but the key behavioral trait is fully disclosed.

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

Conciseness5/5

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

The description is a single sentence with the core behavior front-loaded ('Always returns a tool execution error'). It is concise and contains no unnecessary words or filler.

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?

For a zero-parameter, no-output-schema tool, the description is fully complete. It precisely specifies what the tool does without needing to explain parameters or return values. The purpose is fully captured.

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?

The tool has zero parameters, so the empty schema is fully covered. The description adds no parameter semantics because none are needed. The baseline for 0 params is 4.

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?

The description clearly states the tool always returns a tool execution error via isError true, and explicitly distinguishes this from a JSON-RPC protocol error. This specific verb and resource make the tool's purpose unambiguous and differentiate it from siblings like structured_result or echo_meta.

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

Usage Guidelines2/5

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

The description only states what the tool does, not when or why to use it. It does not reference any testing scenarios or contrast with alternative tools. There is no when-to-use or when-not-to-use guidance.

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

use_handleUse HandleC

Uses a handle returned by create_handle. Unknown handles return a tool execution error.

ParametersJSON Schema
NameRequiredDescriptionDefault
queryYesProbe query to associate with the handle.
handleYesHandle returned by create_handle.

Output Schema

ParametersJSON Schema
NameRequiredDescription
queryYes
handleYes
targetYes
callCountYes

TDQS

C2.9/5.0
Behavior2/5

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

With no annotations, the description carries the full burden. It discloses one behavioral trait: unknown handles return a tool execution error. But it does not describe success behavior, side effects, or whether the operation is read-only or mutating. This is minimal transparency beyond the error condition.

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

Conciseness5/5

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

The description is a single, compact sentence that states the essential dependency on create_handle and the error behavior for unknown handles. It is appropriately sized and front-loaded, with no wasted words.

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?

Despite having an output schema and two well-documented parameters, the description fails to convey the tool's actual operation or purpose. It does not explain what 'uses a handle' accomplishes, making the tool's functionality incomplete for an agent trying to select and invoke it correctly. The error condition is noted, but the success path and overall behavior are absent.

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?

Schema description coverage is 100%, so the baseline is 3. The description reinforces the handle parameter's origin ('returned by create_handle') but adds no additional meaning to 'query' beyond the schema's 'Probe query.' It does not compensate for or enhance the parameter understanding beyond what the schema already provides.

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 'Uses a handle returned by create_handle,' which identifies the tool as the counterpart to create_handle and distinguishes it by its dependency on a prior handle. However, the verb 'uses' is vague—it does not specify what action is performed with the handle or what output is produced, leaving the core purpose unclear.

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?

The description implies that the tool should be used after create_handle, since it requires a handle returned by that tool. It also warns that unknown handles error, which guides the user to provide a valid handle. However, it does not state when to use this tool instead of other siblings (e.g., search, fetch) or specify exclusions.

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

TDQS

A3.7/5.0
Disambiguation5/5

Each tool targets a distinct MCP feature: metadata inspection, structured output, handle-based state, MRTR input, error simulation, resource links, and search/fetch stubs. There is no overlap between their purposes.

Naming Consistency3/5

Names are a mix of verb_noun (echo_meta, create_handle), standalone verbs (search, fetch), and nouns (structured_result, tool_error). While all are snake_case, the varying forms make the naming pattern less predictable than a uniform verb_noun convention.

Tool Count5/5

9 tools is a well-scoped set for a compatibility probe, covering the key MCP client interaction patterns without redundancy or bloat.

Completeness4/5

The tool surface covers essential probe scenarios: metadata, structured content, handles, MRTR, errors, resource links, and search/fetch. Minor gaps exist (e.g., no explicit tool for protocol-level logging or sampling), but the core compatibility checks are well represented.

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