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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real context beyond that: the editor must be settled at expectedRevision and 'source handles authorize edits,' implying authority flows from the source handle. It stops short of describing the retry/replay semantics or rate considerations.

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?

Two tight sentences, front-loaded with the return value before the preconditions. Slightly telegraphic ('source handles authorize edits') borders on ambiguous, keeping it out of 5 territory.

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?

An output schema exists so the PNG return needn't be detailed, and annotations cover the safety profile. The description supplies the sequencing and settled-state precondition an agent needs. Only the authorization phrasing remains mildly underspecified.

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 every parameter is already documented, including the scope enum and the retry semantics of operation_id. The description only lightly reinforces expectedRevision ('settled editor') and the region notion; the baseline 3 applies.

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?

States a concrete verb+resource: returns a PNG of the current editor region. The closing clause ('for visual questions') distinguishes it from sibling text tools like read_context or get_context, though the differentiation is implied rather than explicit.

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?

Gives clear sequencing context ('after a source read') and a precondition ('requires a settled editor at expectedRevision'), which tells the agent when the call will succeed. It does not name an alternative tool or state a when-not condition, so it falls short of a 5.

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