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

Annotations already show readOnly, non-destructive, and idempotent, so the safety profile is known. The description adds behavioral value beyond that: the result is not immediately available, comps land in the background, and the agent should wait roughly 20 seconds. It also scopes the operation to signed-in users.

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 first sentence is efficient and front-loaded: 'the finished result for a scan on their account' immediately communicates the purpose. However, the second sentence is grammatically convoluted, especially 'account.scanId a photo price returned', which makes it needlessly hard for an agent to parse.

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?

Given a read-only tool with one required parameter, strong schema descriptions, and helpful annotations, the description covers the essential async timing and one shape. It doesn't describe fallback or error behaviour, but for a simple 're-read a result' action, the guidance is sufficient.

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 floor is a 3. The description exceeds that floor by explaining when and why a particular scan_id is meaningful: it's the account.scanId returned by price_item and should be re-called after a loading delay. It does not discuss the cost parameter, but the schema already describes it.

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 ('fetch') and named resource ('saved scan's result') with a clear scope: a signed-in user's account. It also distinguishes itself from siblings by referencing the account.scanId from price_item, making it clear this is a follow-up read rather than a comps or price creation tool.

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?

The description explicitly tells the agent whether to call: after price_item reports comps are still loading, wait about 20 seconds and call again, or use it anytime to re-read a saved scan. It doesn't enumerate alternatives like get_sold_comps, but the timing and polling guidance is concrete and actionable.

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