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 the stored-URL output valid for about 24 hours, no inlining over MCP, unchanged page content, rejection of third-party URLs, the absence of an MCP upload channel, and the 20-merges-per-hour rate limit. This is rich behavioral context.

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 long but every sentence earns its place: core action first, then output behavior, exclusions, alternatives, input sourcing, and rate limit. There is no filler and the structure is easy for an agent to parse.

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 tool with no annotations, no input schema, and no output schema, the description is nearly self-sufficient. It covers invocation inputs, constraints, response format via stored URL, alternatives, and operational limits. The only minor omission is the exact response envelope, but the provided detail is sufficient for correct invocation.

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 is empty, so the description is the sole documentation for parameters. It explicitly names `fileUrls`, describes it as an array of URLs in razi.pro's own storage, rejects third-party URLs, and explains the REST API multipart alternative. This more than compensates for the missing schema.

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 a specific verb and resource: 'Concatenate two or more PDFs into a single PDF, in the order supplied, and return the merged file.' It also distinguishes itself from sibling tools like compress_pdf, split_pdf, and images_to_pdf, so an agent can identify the correct operation without inspecting other schemas.

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 gives explicit when-to-use and when-not-to-use guidance: use compress_pdf for compression, split_pdf for page selection, and images_to_pdf when any input is a picture. It also states rejection conditions such as fewer than two files and non-PDF inputs, making alternative selection and invocation rules unambiguous.

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