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MCP Client Compatibility Probe

by kascada

Sonda de compatibilidad de clientes MCP

Pequeño servidor MCP de diagnóstico para comprobar qué soportan realmente los clientes MCP.

El servidor está deliberadamente libre de dependencias y se divide en una lógica central independiente del transporte más un adaptador local stdio. Un futuro adaptador HTTP podrá reutilizar probe-core.mjs para pruebas con ChatGPT Web, OpenAI API o MCP remoto.

El flujo de trabajo previsto es asistido por IA: apunta el asistente/cliente que quieras probar a este repositorio y deja que ejecute la sonda, inspeccione el rastro, cree un archivo de resultados y prepare un commit. En la práctica, eso es un solo prompt.

La visión general informal actual del soporte de clientes está en CLIENT-MATRIX.md. El diseño detallado de las pruebas y las plantillas de resultados están en TESTPLAN.md.

Inicio rápido para evaluadores

Opción A: Un solo prompt

Inicia el asistente o cliente que quieras probar, en un directorio en el que tenga permiso de escritura, y dale esto:

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.

Eso es toda la configuración. A partir de ahí, el asistente clona el repositorio, ejecuta la prueba de humo, registra la sonda como servidor MCP local, ejecuta las interacciones de la sonda, inspecciona el rastro y escribe el archivo de resultados. Solo vuelve a ti para las cosas que realmente no puede hacer por sí mismo: reiniciar el cliente para que cargue la configuración de MCP, invocar cualquier cosa que el cliente exponga solo como acción de usuario y aprobar el push o la pull request.

Esto asume un cliente que pueda ejecutar comandos de shell y leer archivos locales, como Claude Code, Codex CLI, OpenCode o Cursor. Si el tuyo no puede, usa la Opción B.

Opción B: Paso a paso

La misma prueba, explicada paso a paso. Úsala si tu cliente no puede clonar por sí solo, o si quieres ver qué hará la Opción A antes de ejecutarla.

  1. Clona este repositorio.

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

    Se recomienda HTTPS para la mayoría de los evaluadores porque funciona sin una clave SSH configurada. Si ya usas GitHub por SSH, esto es equivalente:

    git clone git@github.com:kascada/mcp-client-compat-probe.git
    cd mcp-client-compat-probe
  2. Abre el directorio clonado en el asistente/cliente compatible con MCP que quieras probar.

  3. Pide al asistente que ejecute PROMPT.md, por ejemplo: Run PROMPT.md. Si el asistente no puede leer archivos locales, pega el contenido completo de PROMPT.md en su lugar.

  4. Sigue solo las indicaciones explícitas para reiniciar el cliente, confirmar la configuración de MCP y aprobar el push/PR.

El asistente debería encargarse del resto:

  • ejecutar npm run smoke

  • ayudar a configurar el servidor MCP stdio local si es necesario

  • ejecutar las interacciones de la sonda

  • inspeccionar el archivo de rastro

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

  • añadir al stage y hacer commit solo de ese archivo de resultados

No hagas commit de archivos de rastro completos por defecto. Los archivos de resultados deben incluir solo pequeños extractos censurados.

Related MCP server: jakegaylor-com-mcp-server

Cómo contribuir con un resultado

Este repositorio es público, lo que significa que cualquiera puede leerlo y clonarlo, pero no hacer push. Clonar no crea un fork ni otorga acceso de escritura, por lo que contribuir con un resultado se hace mediante una pull request desde tu propio fork. El asistente puede hacer esto por ti; el equivalente manual es:

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

Usa tu nombre de cuenta de GitHub como <username>, para que el resultado sea atribuible en la colección compartida.

Si no puedes o no quieres abrir una pull request, también son válidas estas opciones:

  • Abrir un issue y adjuntar el archivo de resultados.

  • Enviar el archivo de resultados directamente al autor del repositorio, junto con la versión del cliente, el sistema operativo y tu configuración de MCP sin secretos.

Archivos

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

Cobertura de la sonda

Métodos MCP implementados:

  • server/discover

  • respuesta de respaldo initialize heredada

  • tools/list

  • tools/call

  • resources/list

  • resources/read

  • resources/templates/list

  • prompts/list

  • prompts/get

  • stub subscriptions/listen

Herramientas:

  • echo_meta: devuelve los argumentos recibidos, _meta, las capacidades del cliente y las observaciones de transporte.

  • structured_result: devuelve texto más structuredContent que coincide con un outputSchema.

  • create_handle: crea un manejador de estado explícito.

  • use_handle: usa un manejador de create_handle.

  • needs_form_input: devuelve resultType: "input_required" hasta que se reintente con inputResponses.

  • tool_error: devuelve un error de ejecución de herramienta mediante isError: true.

  • resource_link_result: devuelve un elemento de contenido resource_link.

  • search: stub de búsqueda compatible con ChatGPT.

  • fetch: stub de fetch compatible con ChatGPT.

Prueba de humo

Ejecuta desde este directorio:

npm run smoke

O sin npm:

node scripts/smoke-stdio.mjs

La prueba de humo escribe su rastro en:

/tmp/mcp-probe-smoke.ndjson

Registro de rastro

El servidor nunca escribe diagnósticos en stdout, porque stdout debe contener solo mensajes MCP JSON-RPC. Los diagnósticos van a stderr y al archivo de rastro.

Ruta de rastro por defecto:

/tmp/mcp-probe.ndjson

Ruta de rastro de OpenCode desde opencode.json:

/tmp/mcp-probe-opencode.ndjson

Cada línea es JSON con:

  • ts: marca de tiempo

  • pid: ID del proceso del servidor

  • direction: in o out

  • payload: carga útil JSON-RPC

Prueba con OpenCode

Este directorio contiene un opencode.json aislado:

{
  "$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"
      }
    }
  }
}

Inicia OpenCode desde este directorio para que cargue la configuración local:

opencode

Luego pregunta:

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

Prompts adicionales útiles:

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.

Interpreta el rastro:

  • server/discover presente: se usa la sonda de descubrimiento MCP moderna.

  • initialize presente: se usa la ruta de handshake heredada.

  • _meta.io.modelcontextprotocol/protocolVersion presente: se envía la versión de protocolo por solicitud.

  • _meta.io.modelcontextprotocol/clientCapabilities.elicitation presente: el cliente declara soporte de elicitación.

  • resources/list o prompts/list presente: el cliente consulta activamente primitivas que no son herramientas.

  • Reintento después de input_required: se maneja el flujo MRTR/Elicitation.

OpenCode lee la configuración al inicio. Reinicia OpenCode después de cambiar opencode.json o los archivos del servidor.

Prueba con Codex CLI o ChatGPT Desktop

El mismo servidor stdio local puede ser usado por Codex CLI, la aplicación de escritorio de ChatGPT y la extensión Codex IDE, porque soportan servidores MCP locales.

Ejemplo de registro de Codex CLI desde este directorio:

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

Luego usa /mcp en Codex para inspeccionar los servidores activos y pide las mismas herramientas de sonda que arriba.

Para la aplicación de escritorio de ChatGPT, añade un nuevo servidor MCP en Configuración con:

  • Nombre: probe

  • Tipo: STDIO

  • Comando: node

  • Args: ruta absoluta a stdio-server.mjs

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

Ruta de ChatGPT Web y OpenAI API

ChatGPT Web no puede iniciar directamente un servidor stdio local ni leer la configuración local de Codex/OpenCode. Para pruebas con ChatGPT Web o OpenAI API, añade un adaptador HTTP remoto más adelante.

El diseño actual mantiene esa ruta abierta:

  • probe-core.mjs no tiene comportamiento específico de stdio.

  • stdio-server.mjs solo adapta JSON-RPC delimitado por nuevas líneas a handleJsonRpc.

  • Un futuro http-server.mjs puede llamar al mismo handleJsonRpc y pasar cabeceras HTTP en el objeto de transporte.

  • Las herramientas existentes search y fetch ya siguen la forma simple compatible con ChatGPT con structuredContent y resultados respaldados por URL.

Comprobaciones específicas de HTTP para añadir más adelante:

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

  • cabeceras estáticas/Bearer

  • comportamiento de OAuth

  • x-mcp-header de los parámetros de la herramienta

  • comportamiento de respuesta HTTP transmisible

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.

Maintenance

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