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

Although annotations already declare readOnly, idempotent, non-destructive and closed-world, the description adds substantial context beyond them: it enumerates what the preview returns, describes the two-thirds similarity copy-refusal rule, and explains the human review within 3 days. It also makes explicit that the tool never shares on the user's behalf, which is exactly the safety nuance an agent needs.

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 key point ('writes nothing') is front-loaded, and every clause contributes operational detail. The sentence is long and heavily parenthetical, which makes it dense rather than perfectly crisp, but it is not padded.

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?

With no output schema, the description must explain return values, and it does: the picture drawn, what leaves and stays, the texts, the closest existing template and copy threshold, and the permission implied by sharing. It also explains share_url's role, leaving nothing important for an agent to infer.

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% and the enum already documents the three modes, so the baseline is 3. The description still adds meaning by tying words: false to authors' texts staying behind and explaining that style mode reuses colours and type 'on a film of ours,' which goes beyond the schema's phrasing.

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?

Names a specific verb (shows what would leave) and resource (sharing a film or one of the user's pieces), and immediately separates itself from the real share action by stating 'writes nothing' and 'You never share in their place.' An agent can tell this is a dry-run preview rather than a mutation, even though no sibling share tool exists.

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?

Establishes clear context: use it to see what sharing would send, with a branch for as: piece, and points to share_url for actually opening the editor's share window. It stops short of explicitly naming when not to use it or comparing to a sibling such as shared_for_view, but the workflow guidance is strong.

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