MCP Server Box

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 discloses that the tool returns a dictionary with 'thumbnail URL or message if not available,' which hints at possible failure modes. However, it lacks details on authentication needs, rate limits, or what specific conditions cause 'not available' (e.g., unsupported file formats, permissions). This partial disclosure is adequate but leaves gaps for a read operation.

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 efficiently structured: a clear purpose statement followed by bullet-like sections for 'Args' and 'Returns.' Each sentence adds value—no redundancy or fluff. It's front-loaded with the core function, and parameter details are organized for quick parsing, 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?

Given 6 parameters with 0% schema coverage and no annotations, the description does an excellent job explaining inputs and hinting at output behavior. However, it lacks details on error conditions (e.g., what 'message if not available' entails) and doesn't reference the output schema. For a tool with moderate complexity, this is mostly complete but could be slightly enhanced with more behavioral 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 description coverage is 0%, so the description must compensate fully. It does so by detailing all 6 parameters: 'file_id' (required), 'extension' (optional, with allowed values 'png' or 'jpg'), and min/max height/width (optional, with pixel ranges 32-320). This adds crucial meaning beyond the bare schema, including defaults and constraints, making parameters well-understood.

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's purpose: 'Retrieve the URL for a thumbnail image of a file.' It specifies the verb ('retrieve') and resource ('thumbnail image of a file'), making the intent unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'box_file_thumbnail_download_tool' (which downloads the thumbnail vs. getting a URL), so it doesn't reach the highest clarity level.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools (e.g., 'box_file_thumbnail_download_tool' for downloading thumbnails directly) or contextual prerequisites like file types that support thumbnails. The agent must infer usage from the tool name and parameters alone.

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