snapshot

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

With no annotations, the description carries the full burden and does well: it discloses the return shape (refs plus value/checked/selected/expanded/disabled state), the iframe ref-routing rule (@fN refs pass through unchanged), and a cost signal ('Cheap'). It omits any note on output size limits or how stale a snapshot becomes, which is the only gap.

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?

Three dense sentences, each earning its place: what it returns, when to call it, and the iframe ref caveat. The most decision-relevant guidance (call before click/type) is front-loaded.

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 zero-required-param read tool with no output schema, the description adequately covers return content, usage, and the iframe edge case. Only minor omissions remain (no mention of snapshot staleness or size behavior).

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 description coverage is 100%, so tabId and spaceId are already documented in the schema. The description adds nothing about parameter usage, so 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 specific verb ('Capture') and resource ('the current page as a compact list of interactive elements with refs and state'), and enumerates the returned content (dialogs, alerts, text excerpt). This clearly distinguishes it from siblings like screenshot, read_text, and eval.

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 an explicit trigger ('Call this before any click/type') and names the alternatives it should beat ('prefer it over screenshots or eval'). The agent knows both when to use it and what to use instead.

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