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

Beyond the readOnly/idempotent annotations, it discloses plan-gated behavior (null fields listed in `locked`, `estimates` meaning sales/visits/traffic, `lockedCount` for higher plans), an explicit handling rule ('Say the data is on a higher plan; never estimate it yourself'), and the side-effect-free nature ('Returns data only: nothing is shown to the user yet').

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?

It is dense but front-loaded, leading with what the tool returns before plan caveats and the show-call workflow. Every sentence carries distinct information, though the plan-gating detail could be tightened slightly.

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 still covers the return shape (dated captures, screenshots, offers, locked fields), the plan-dependent window, and the required follow-up show call, leaving no significant gap for correct invocation.

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 67%, and the required parameter `sitePageId` has no description in either the schema or the description text. The description explains return fields (`locked`, `lockedCount`) rather than input parameters, so it does not compensate for the undocumented required parameter.

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?

The description states a specific verb and resource with clear scope: 'How one landing page changed over time: its dated captures, newest first, each with a screenshot and the offers read from it.' This is plainly distinguishable from the sibling sightglass_get_site_page (current page state) because it is explicitly framed as a time-series history.

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?

It gives concrete triggering intents ('what did they change on this page', 'when an offer appeared or deepened') and routes the follow-up step explicitly to sightglass_show with resultId. It does not name a competing sibling or state when NOT to use this tool, so it falls short of a full 5.

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