MCP Client Compatibility Probe
MCP 客户端兼容性探针
用于检查 MCP 客户端实际支持情况的小型诊断工具。
该服务器刻意保持零依赖,并将传输无关的核心逻辑与本地 stdio 适配器分离。未来的 HTTP 适配器可以复用 probe-core.mjs,用于 ChatGPT Web、OpenAI API 或远程 MCP 测试。
预期工作流程是 AI 辅助式的:让您想测试的助手/客户端指向本仓库,由它运行探针、检查跟踪记录、创建结果文件并准备提交。实际操作中,这只是一个提示词。
当前非正式的客户端支持概览见 CLIENT-MATRIX.md。详细的测试设计和结果模板见 TESTPLAN.md。
测试人员快速上手
方案 A:单条提示词
启动您想测试的助手或客户端,将其放在允许写入的目录中,然后给它这条提示词:
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.这就是全部设置。接下来助手会自行克隆仓库、运行冒烟测试、将探针注册为本地 MCP 服务器、执行探针交互、检查跟踪记录并写入结果文件。它只会把确实无法自行完成的事情交回给您,例如:重启客户端以加载 MCP 配置、调用客户端仅以用户操作方式暴露的功能,以及批准推送或拉取请求。
此方案要求客户端能够运行 shell 命令并读取本地文件,例如 Claude Code、Codex CLI、OpenCode 或 Cursor。如果您的客户端不具备这些能力,请使用方案 B。
方案 B:逐步操作
与上述相同的测试,但以逐步方式展开。如果您的客户端无法自行克隆仓库,或者您想先看看方案 A 会做什么,请使用此方案。
克隆本仓库。
git clone https://github.com/kascada/mcp-client-compat-probe.git cd mcp-client-compat-probe大多数测试人员推荐使用 HTTPS,因为它无需配置 SSH 密钥即可工作。如果您已经通过 SSH 使用 GitHub,则以下命令等效:
git clone git@github.com:kascada/mcp-client-compat-probe.git cd mcp-client-compat-probe在您想测试的支持 MCP 的助手/客户端中打开克隆下来的目录。
让助手运行
PROMPT.md,例如:Run PROMPT.md。 如果助手无法读取本地文件,请将PROMPT.md的完整内容粘贴给它。只遵循其中关于客户端重启、MCP 配置确认以及推送/拉取请求批准的明确提示。
其余工作应由助手处理:
运行
npm run smoke如有需要,帮助配置本地
stdioMCP 服务器执行探针交互
检查跟踪记录
写入
results/<client>-<username>-<date>.md仅暂存并提交该结果文件
默认情况下不要提交完整的跟踪文件。结果文件应只包含少量经过脱敏的摘录。
Related MCP server: jakegaylor-com-mcp-server
贡献结果
本仓库是公开的,这意味着任何人都可以读取和克隆它,但不能直接推送。因此,贡献结果需要通过您自己的 fork 发起拉取请求。助手可以为您完成此操作;手动操作的等效方式是:
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请使用您的 GitHub 用户名作为 <username>,以便在共享集合中标注结果来源。
如果您不想或无法发起拉取请求,以下两种方式也同样可以:
提交 issue 并附上结果文件。
将结果文件直接发送给仓库作者,同时附上客户端版本、操作系统以及您的 MCP 配置(记得删除其中的机密信息)。
文件
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探针覆盖范围
已实现的 MCP 方法:
server/discover旧版
initialize回退响应tools/listtools/callresources/listresources/readresources/templates/listprompts/listprompts/get桩
subscriptions/listen
工具:
echo_meta:返回收到的参数、_arguments、客户端能力以及传输层观察信息。structured_result:返回文本以及匹配outputSchema的structuredContent。create_handle:创建一个显式的状态句柄。use_handle:使用create_handle创建的状态句柄。needs_form_input:返回resultType: "input_required",直到使用inputResponses重试。tool_error:通过isError: true返回工具执行错误。resource_link_result:返回一个resource_link内容项。search:兼容 ChatGPT 的搜索桩。fetch:兼容 ChatGPT 的抓取桩。
冒烟测试
从本目录运行:
npm run smoke或者不使用 npm:
node scripts/smoke-stdio.mjs冒烟测试将其跟踪记录写入:
/tmp/mcp-probe-smoke.ndjson跟踪日志
服务器绝不会向 stdout 写入诊断信息,因为 stdout 必须只包含 MCP JSON-RPC 消息。诊断信息写入 stderr 和跟踪文件。
默认跟踪路径:
/tmp/mcp-probe.ndjsonOpenCode 的跟踪路径来自 opencode.json:
/tmp/mcp-probe-opencode.ndjson每一行都是 JSON 格式,包含:
ts:时间戳pid:服务器进程 IDdirection:in或outpayload:JSON-RPC 消息内容
使用 OpenCode 测试
本目录包含一个独立的 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"
}
}
}
}请从本目录启动 OpenCode,以便它加载本地配置:
opencode然后询问:
Nutze das probe echo_meta Tool und zeige mir, welche MCP-Metadaten du gesendet hast.其他有用的提示词:
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.解读跟踪记录:
存在
server/discover:使用了现代 MCP 发现探针。存在
initialize:走的是旧版握手路径。存在
_meta.io.modelcontextprotocol/protocolVersion:发送了按请求的协议版本。存在
_meta.io.modelcontextprotocol/clientCapabilities.elicitation:客户端声明支持 elicitation。存在
resources/list或prompts/list:客户端会主动查询非工具类原语。在
input_required之后出现重试:MRTR/Elicitation 流程已处理。
OpenCode 在启动时读取配置。修改 opencode.json 或服务器文件后,需要重启 OpenCode。
使用 Codex CLI 或 ChatGPT 桌面版测试
同一个本地 stdio 服务器也可用于 Codex CLI、ChatGPT 桌面应用和 Codex IDE 扩展,因为它们都支持本地 MCP 服务器。
从本目录进行 Codex CLI 注册示例:
codex mcp add probe --env MCP_PROBE_TRACE=/tmp/mcp-probe-codex.ndjson -- node stdio-server.mjs然后在 Codex 中使用 /mcp 查看活动服务器,并询问相同的探针工具。
对于 ChatGPT 桌面应用,请在设置中添加新的 MCP 服务器:
名称:
probe类型:
STDIO命令:
node参数:
stdio-server.mjs的绝对路径环境变量:
MCP_PROBE_TRACE=/tmp/mcp-probe-chatgpt-desktop.ndjson
ChatGPT Web 与 OpenAI API 路径
ChatGPT Web 无法直接启动本地 stdio 服务器,也无法读取本地 Codex/OpenCode 配置。如需在 ChatGPT Web 或 OpenAI API 上进行测试,后续需要添加远程 HTTP 适配器。
当前设计为这条路径保留了扩展空间:
probe-core.mjs不包含任何 stdio 特有的行为。stdio-server.mjs仅将换行分隔的 JSON-RPC 适配到handleJsonRpc。未来的
http-server.mjs可以调用相同的handleJsonRpc,并在传输对象中传递 HTTP 头。现有的
search和fetch工具已经采用简单的 ChatGPT 兼容形态,带有structuredContent和基于 URL 的结果。
后续需要补充的 HTTP 专项检查:
MCP-Protocol-Version、Mcp-Method、Mcp-Name静态/Bearer 认证头
OAuth 行为
来自工具参数的
x-mcp-headerStreamable HTTP 响应行为
Available Tools
9 toolscreate_handleCreate HandleA
Creates an explicit short-lived probe handle to test stateless multi-call tool design.
| Name | Required | Description | Default |
|---|---|---|---|
| target | Yes | Target system or scenario for the handle. |
Output Schema
| Name | Required | Description |
|---|---|---|
| handle | Yes | |
| target | Yes | |
| expiresInSeconds | Yes |
TDQS
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.
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.
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.
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.
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.
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.
| Name | Required | Description | Default |
|---|---|---|---|
| message | No | Any message to echo back. |
Output Schema
| Name | Required | Description |
|---|---|---|
| meta | Yes | |
| observed | Yes | |
| arguments | Yes |
TDQS
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.
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.
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.
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.
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.
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 DocumentARead-only
ChatGPT-compatible read-only fetch stub. Retrieves full text for an ID returned by search.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Document ID returned by search. |
Output Schema
| Name | Required | Description |
|---|---|---|
| id | Yes | |
| url | Yes | |
| text | Yes | |
| title | Yes | |
| metadata | No |
TDQS
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.
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.
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.
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.
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.
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.
| Name | Required | Description | Default |
|---|---|---|---|
| topic | Yes | Topic for the requested follow-up input. |
TDQS
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.
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.
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.
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.
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.
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.
resource_link_resultResource Link ResultC
Returns a resource_link content item pointing at a probe resource.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It only states the return type and points at a probe resource, but gives no information about side effects, error behavior, permissions, or whether the operation is read-only. This is minimal transparency.
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?
The description is a single sentence with no filler. It is appropriately concise and front-loaded, stating the core behavior immediately.
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?
With no output schema and no annotations, the description is too sparse. It does not explain what a resource_link content item is, what a probe resource is, or how to handle the result. This leaves significant gaps for an agent selecting among sibling tools.
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 has zero parameters, so the description has no need to explain parameter syntax or semantics. The baseline for zero parameters is 4, and the description does not miss anything here.
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?
The description clearly states the tool returns a resource_link content item, which is specific and differentiates it somewhat from generic tools. However, it does not clarify what a 'probe resource' is or how this differs from sibling result tools 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.
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 lacks any mention of prerequisites, exclusions, or sibling tools, leaving the agent without a basis for selection.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
searchSearch Probe DocumentsARead-only
ChatGPT-compatible read-only search stub. Returns result IDs, titles, and URLs. Use fetch to retrieve full text.
| Name | Required | Description | Default |
|---|---|---|---|
| query | Yes | Search query. |
Output Schema
| Name | Required | Description |
|---|---|---|
| results | Yes |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation already covers safety, and the description adds context by stating it is a 'stub' and returns specific fields (IDs, titles, URLs). This provides behavioral insight beyond the annotation, though it does not elaborate on limitations like pagination or result counts.
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?
The description is a single concise sentence that states purpose, output, and usage guidance without any redundancy. It is front-loaded and immediately clear.
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?
Given the simple one-parameter search tool, the description covers its return values and relationship to fetch. The presence of an output schema and annotations reduces the burden, and the description fills the essential gaps.
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 schema has 100% coverage for the single 'query' parameter with a basic description. The tool description does not add any additional semantics beyond the schema, so baseline 3 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?
The description clearly states that the tool performs a search, returns result IDs, titles, and URLs, and is specifically for probe documents. It distinguishes from the sibling tool 'fetch' which retrieves full text, making the purpose unambiguous.
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?
Explicitly says 'Use fetch to retrieve full text,' providing a clear alternative and when to use another tool. It also labels the tool as read-only, suggesting it is for search queries only, not for retrieval or modification.
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.
| Name | Required | Description | Default |
|---|---|---|---|
| label | No | Optional label for the generated result. |
Output Schema
| Name | Required | Description |
|---|---|---|
| label | Yes | |
| answer | Yes | |
| nested | Yes |
TDQS
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.
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.
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.
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.
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.
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.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
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.
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.
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.
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.
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.
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.
| Name | Required | Description | Default |
|---|---|---|---|
| query | Yes | Probe query to associate with the handle. | |
| handle | Yes | Handle returned by create_handle. |
Output Schema
| Name | Required | Description |
|---|---|---|
| query | Yes | |
| handle | Yes | |
| target | Yes | |
| callCount | Yes |
TDQS
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.
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.
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.
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.
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.
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
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.
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.
9 tools is a well-scoped set for a compatibility probe, covering the key MCP client interaction patterns without redundancy or bloat.
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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