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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered. The description adds genuinely new information beyond those: the estimate is not binding because 'Admission rechecks price and balance' at submit time. Missing is any statement about units or error behavior for invalid dimensions.

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 short sentences, front-loaded with the action and inputs, followed by the one caveat that matters. No filler.

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?

There is no output schema, so the description should at least hint at the return shape (a credit count), and it does say 'credits'. However, units for the three required numeric parameters and the non-binding nature of the result relative to submit_subtitle_task are only partially covered, leaving real gaps for a 3-required-param tool.

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 0% and the description only echoes the property names ('video width, height and duration'). Critical semantics — whether width/height are pixels and duration is seconds, and in what unit the resulting credits are expressed — are absent from both schema and description.

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 (Estimate) and resource (subtitle-removal credits) and names the inputs that drive it (width, height, duration). It is clearly a pre-flight cost calculator, distinguishable from submit_subtitle_task, though it never names that sibling explicitly.

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 phrase 'before submitting' implies the usage context, but no alternative tool is named and no when-not-to-use condition is given. An agent can infer this precedes submit_subtitle_task, but must do the inferring.

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