Take screenshot

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

Annotations only give readOnlyHint=false and openWorldHint=false; the description adds the real behavioral facts an agent needs: the file is written into the screenshot directory and the response includes the path. It also discloses the conditional image return ('unless returnImage is false or the image is very large'), which explains an otherwise surprising omission. Minor gap: silent about filename collisions/overwrite behavior, which matters for a write.

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?

One sentence, front-loaded with the action and artifact, then the return contract. Nothing redundant with the title or schema is repeated needlessly.

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?

No output schema exists, and the description carries the return contract (file path plus conditionally the image). With only three fully documented optional params and explicit side-effect disclosure, nothing essential is missing for an agent to call this 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?

Schema coverage is 100%, so the baseline is 3 and the schema already documents all three params. The description adds genuine nuance beyond the schema: returnImage's suppression is conditional not just on the flag but also on image size, and it explains the context-saving motive. That is value above the structured fields.

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?

Specific verb ('Capture a PNG'), specific resource ('the current page'), and it names both capture modes (full scrollable page vs viewport) plus where the artifact lands. That is enough to separate it from get_page_snapshot, which by contrast implies text/DOM inspection rather than an image artifact.

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 implies visual evidence capture and mentions the context trade-off for returnImage, but it never states when to reach for this versus get_page_snapshot or start_recording, nor any prerequisites (page loaded, navigation settled). Usage must be inferred.

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