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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds useful behavioral context: it returns only the URL rather than price data, requires an exact slug, and should not be used for quoting. It does not describe failure behavior for a bad slug, which keeps it short of a 5.

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 output type and format are front-loaded in the first clause, followed by usage conditions, prerequisites, exclusions, and safety traits. Every sentence adds a distinct decision-relevant fact with 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?

For a single-parameter, read-only URL-returning tool with no output schema, the description supplies the return format, the precondition, the discovery alternatives, and the boundary against get_unit_price. Nothing needed to select or invoke it correctly is missing.

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%, including the example 'persil-color-gel-100-prani', so the schema already carries the baseline semantics. The description adds meaning by emphasizing that the slug must be exact and by naming search_cite_answers and get_unit_price as discovery paths, which goes beyond the schema text.

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: return the 1200×630 PNG price-card URL for a Cite answer. It explicitly distinguishes the output from JSON price fields and from get_unit_price, so an agent can identify the tool without inspecting the schema.

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 explicit when-to-use guidance ('when the agent needs an image, not JSON price fields') and when-not-to-use guidance ('does not replace get_unit_price for quoting €/unit or buy_url'). It also names the sibling tools for discovering the required slug, leaving no routing ambiguity.

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