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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuinely useful behavior: the operation is free and performs no AI call, which is a cost/latency characteristic not expressed anywhere in structured fields, and it sketches the return payload ('numbers and photo').

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 with no filler; the verb+resource comes first and the cost note follows. Every clause carries information.

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 one-parameter read with no output schema, the description covers what is fetched ('numbers and photo') and the cost model. Minor gaps remain: it doesn't say what happens for a nonexistent page or the exact response shape, but nothing essential blocks a correct call.

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 single parameter's 'Page URL or slug' description already covers both accepted forms, which is exactly what the tool description repeats. Baseline 3 is appropriate since the schema does the work.

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 ('Fetch') and resource ('the numbers and photo for an existing VisualizeVolume page'), and the input route (URL or slug) is named. It stops short of explicitly distinguishing itself from the sibling 'visualize', though 'no AI call' hints at the difference.

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?

'Existing' page and 'Free; no AI call' imply this is the cheap retrieval path versus the generative sibling, but the description never names 'visualize' or states when not to use this tool. Usage is only implied, not spelled out.

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