Server Quality Checklist

Tool Scores

• generate_thumbnailA
  4.4/5.0
  Behavior5/5

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

  With no annotations, the description carries the full burden and does an excellent job: it discloses the returned data (inline image plus metadata fields), the public CDN URL, the authentication requirement, and the account-plan constraints for `hd` models. This is far beyond typical descriptions.

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

  Conciseness4/5

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

  The description is well-structured with clear sections (purpose, usage, return, auth) and is not excessively long. It earns its length by covering both usage and behavioral details, though it could be slightly shorter by moving auth instructions elsewhere.

  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?

  Given the tool has no output schema, the description compensates by explicitly describing the return format and metadata. It also covers prerequisites, costs, and model selection, making it self-contained for an agent to use correctly.

  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 already covers all parameters with rich descriptions, so the baseline is 3. The description adds some operational context (e.g., using `imageUrl` rather than base64), but it does not substantially elaborate on parameter meaning beyond the schema.

  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 opens with a specific verb ('Generate') and resource ('thumbnail / social share image'), and further clarifies by listing concrete platforms (YouTube, Instagram, etc.). This clearly distinguishes it from the auth-focused sibling tools `login` and `logout`.

  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?

  It explicitly states when to use the tool ('Use this when...') with a list of use cases, and it mentions the prerequisite of an API key and the `login` alternative for auth. However, it does not explicitly describe when not to use it or mention alternative thumbnail-generation tools.

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

• loginA
  4.8/5.0
  Behavior5/5

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

  With no annotations, the description fully discloses behavior: blocks up to 30s, returns 'still waiting' if not yet consented, callback server persists for 15 minutes across calls, and saves key to a config file. This gives the agent actionable expectations about timeouts and retry semantics.

  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 well-structured with three logical sections: purpose/action, when to call, and behavioral notes. Each sentence adds necessary information without fluff. The bulleted usage guidelines improve scannability.

  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 description covers what the tool does, when to call, and key edge cases (blocking, 'still waiting', server lifetime). However, since there is no output schema, it would be helpful to specify what a successful response looks like, not just the pending case. This is a minor gap that keeps it from a perfect score.

  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 takes zero parameters, so the schema already fully covers parameter semantics (100% coverage). Baseline for 0 params is 4, and the description doesn't need to add parameter info. It appropriately omits any parameter discussion.

  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's purpose: 'Sign the MCP server in to ThumbAPI' with a specific verb and resource. It also provides concrete details about the process (opens browser, asks consent, saves API key), which distinguishes it from siblings like logout and generate_thumbnail.

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

  Usage Guidelines5/5

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

  Explicit 'Call this tool when' section lists two clear triggering conditions: user requests authentication, or generate_thumbnail returns 'no API key found'. This provides unambiguous guidance on when to use the tool and implicitly contrasts with logout for the opposite action.

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

• logoutA
  4.9/5.0
  Behavior5/5

  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 openly states that the tool modifies a specific local file and explicitly notes that it does NOT revoke the key on the server, giving the agent a clear understanding of the tool's exact effects and limitations.

  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 sentences that front-load the primary action and immediately follow with a critical clarification. Every word contributes meaning, with no redundancy 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?

  The tool is simple (no parameters, no output schema), and the description covers all necessary context: what it does, where it operates, and what it intentionally does not do. This is a complete and self-contained description.

  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 parameter explanation is unnecessary. Per the rubric, a baseline of 4 is appropriate when there are no parameters and the description is clear about the tool's function.

  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?

  Description states a specific action ('Remove the saved ThumbAPI API key from ~/.thumbapi/config.json') and clearly distinguishes itself from server-side revocation with the explicit note 'Does not revoke the key on the server.' This makes the tool's purpose unmistakable and separates it from sibling tools like login and generate_thumbnail.

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

  Usage Guidelines5/5

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

  The description explicitly clarifies when this tool is appropriate (local logout) and when it is not (server-side revocation, which is a separate dashboard action). This provides clear usage boundaries and prevents misuse.

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