Add a screenshot

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

With no readOnly/idempotent/destructive hints, the description carries the behavioral burden and does so well: it discloses magic-number validation, CDN storage, supported formats, the 5MB limit, and append ordering. It doesn't cover failure modes or idempotency, but the disclosed side effects are sufficient for a safe call.

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?

Five compact sentences front-load the purpose and then add only high-value operational details. No filler or repetition of schema descriptions.

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 4-param, no-output-schema mutation tool with no annotations, the description covers input selection, format constraints, ordering behavior, and the alt-text requirement. An agent has everything needed to 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?

Schema coverage is 100%, so the baseline is 3, but the description adds meaningful semantics: exactly one of url/base64 is required, the https requirement and data URL acceptability, format/size limits, and the strong directive to always write alt text. This is substantial value beyond the 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?

Describes a specific action ('Adds one screenshot'), resource ('a game you own'), and a key constraint ('up to 6 per game'). This clearly differentiates from sibling tools like remove_screenshot, reorder_screenshots, and set_cover.

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?

States that screenshots are appended in call order and explicitly names reorder_screenshots as the alternative for changing order, which is concrete usage guidance. It does not explicitly contrast with remove_screenshot or set_cover, but the ownership and upload context implies when this tool applies.

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