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

Annotations only mark this read-only and open-world; the description adds the operational facts those annotations cannot: the free tier is limited, paid upgrades exist, an Authorization Bearer header is required for full results, and the quota is enforced per IP per UTC day (1 free, 20 for shared ASN pools, 20 globally). Auth, cost and rate limits are exactly the behavioural details an agent needs before calling.

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?

Front-loaded with the action and scope, then the limits and billing. Every sentence carries information, though the x402/Apify billing clause is dense and slightly interrupts the sequence of functional constraints.

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?

A one-parameter tool with no output schema; the description covers input limits, auth requirements, quota behaviour and what is returned ('a limited free result and paid upgrade links'). Nothing material is missing for a 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?

With a single parameter at 100% schema coverage, the schema already defines the url field, so the baseline is 3. The description reinforces the 'one public image URL' constraint and the size/singularity limit, which slightly improves on the schema's own wording without adding format or syntax detail.

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 and resource: 'Reads text from one public image URL with AI.' That is unambiguously OCR, which separates it from the neighbouring image tools such as upscale_image, resize_image and remove_image_background. The scope word 'one' is stated up front rather than left implicit.

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?

'Use for one url. Not for batch work or unrestricted monitoring' gives the positive case and the explicit exclusions in consecutive sentences. No sibling alternative is named, but the boundary conditions are stated directly enough that an agent knows when not to call this.

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