postfast-mcp

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

With no annotations provided, the description carries full burden. It discloses that the tool returns signed URLs for uploads and that subsequent steps involve PUT requests and using keys in another tool, which adds useful behavioral context. However, it lacks details on permissions, rate limits, or error handling, leaving gaps for a mutation-related tool.

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 front-loaded with the core purpose in the first sentence, followed by actionable next steps. Every sentence earns its place by providing essential guidance without redundancy, making it highly efficient 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 no annotations and no output schema, the description does well by explaining the tool's role in a multi-step process (get URLs, upload, use in create_posts). However, it could be more complete by mentioning authentication needs or response format, though the lack of output schema is mitigated by the clear workflow description.

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 schema fully documents both parameters. The description does not add any parameter-specific semantics beyond what the schema provides, such as explaining why contentType is required or count limits exist. Baseline 3 is appropriate as the schema does the heavy lifting.

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 'Get' and the resource 'signed upload URLs for media files', specifying the exact purpose. It distinguishes from siblings like 'upload_media' by focusing on URL generation rather than direct upload, and from 'create_posts' by handling pre-upload steps.

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?

It explicitly states when to use this tool: to obtain URLs for uploading files, and what to do next (upload via PUT, then use the key in create_posts). This provides clear context and distinguishes it from alternatives like direct upload tools, though it doesn't explicitly name when not to use it.

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