Screen MCP

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It effectively describes the chunk-fetching behavior and reconstruction process, but lacks details on error handling, rate limits, or authentication needs. It doesn't contradict any annotations, but could be more comprehensive for a tool with no annotation support.

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 perfectly front-loaded with the core purpose in the first sentence, followed by essential usage instructions. Every sentence earns its place by providing critical guidance without any wasted words or redundancy.

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 tool's moderate complexity (chunked data retrieval), no annotations, and the presence of an output schema (which handles return values), the description is largely complete. It covers purpose, sequencing, and reconstruction, though could benefit from mentioning error cases or performance considerations.

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 schema has 0% description coverage for its 2 parameters, so the description must compensate. It explains that chunk_index should range from '0 to total_chunks-1' and that timeline_id identifies a session, adding crucial context beyond the bare schema. However, it doesn't specify the format or constraints for timeline_id.

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 specific action ('Return one JSON text chunk') and resource ('for a timeline session'), distinguishing it from siblings like get_timeline_manifest (which provides metadata) and get_screenshot_chunk (which handles screenshots). It precisely defines the tool's role in fetching data chunks.

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 this tool ('Use this after get_timeline_manifest') and provides clear sequencing instructions ('fetch chunks from chunk_index=0 to total_chunks-1 in order'). It distinguishes usage from the manifest-fetching sibling and implies alternatives for non-chunk operations.

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