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

Beyond the readOnly/openWorld annotations, the description adds materially useful traits: metadata-only output (no binary payload), a free-license restriction that affects result eligibility, and a paid-call model with failure not charged. It stops short of rate limits or result-count/pagination behavior, but the cost and content-scope disclosures are the kind of context annotations cannot carry.

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 sentences, both front-loaded: capability and return shape first, then output restriction and price. Dense but no filler; the parenthetical payment-brand list is slightly heavy but is operationally relevant to an agent that must pay.

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?

With only two simple params, no nesting, and an output schema present, the description covers the remaining agent-facing unknowns (auth-free access, metadata vs bytes, licensing filter, cost and charge semantics). Only query-syntax depth and result-count behavior are left implicit.

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 100% — both 'q' (1-200 chars) and 'limit' (1-20, default 5) are documented in the schema. The description adds no syntax, query-operator, or formatting detail beyond that, so the baseline 3 applies.

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 ('Wikimedia Commons image search') and pins down the source protocol ('MediaWiki API, public, no key'), which none of the news/article siblings cover. It also enumerates the returned fields, so an agent knows exactly what it gets without opening the output 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?

Usage is implied rather than stated: 'free-licensed files' and 'not image bytes' tell the agent what class of task this fits, and no-key/public notes remove auth prerequisites. However, there is no explicit when-to-use or when-not-to-use guidance and no named alternative among the many sibling search tools.

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