Annotate a PDF

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

Annotations already indicate destructiveHint=true and readOnlyHint=false. The description adds that it overwrites the output file, returns JSON with status/error for out-of-range pages or coordinates, and explains the coordinate system. This provides useful context beyond annotations, though it does not detail potential side effects like file locking.

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 three sentences plus a brief usage note, conveying all essential information without redundancy. It front-loads the core action and follows with behavior and alternatives, making it efficient and easy to process.

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 detailed input schema and annotations, the description covers all necessary context: purpose, behavior, error handling, coordinate system, and alternatives. It is sufficiently complete for an agent to select and invoke the tool correctly.

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?

Input schema has 100% coverage, but the description adds value by explaining the return format ({status, annotation_type} or {error, code}) and clarifying that width/height only apply to 'highlight'. This goes beyond the schema descriptions, compensating for the high coverage baseline.

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 stamps a sticky note or highlight onto an existing PDF page, with specific verb 'stamp' and resource 'page of an existing PDF'. It distinguishes from sibling tools by mentioning manipulate_pdf for page reordering and create_pdf for authoring new PDFs, 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?

The description explicitly states when to use: 'Use this to mark up a document.' It provides clear alternatives: 'To reorder/rotate/overlay whole pages use manipulate_pdf; to author a new PDF use create_pdf.' It also notes that output_path is overwritten, guiding correct invocation.

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