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

Annotations already declare read-only, idempotent, open-world, non-destructive, so the description focuses on value-add: zero credit cost, plan restriction, and the important caveat that Google ads come without their text. It also lists the return fields (advertiser, headline, text, link), removing ambiguity about output shape despite no output schema.

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-loads the core purpose in the first sentence, then adds short constraint sentences. Parenthetical platform details make the first sentence dense, but every clause carries information; nothing is wasted.

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 4-parameter read-only tool with full schema coverage and annotations, the description covers cost, eligibility, platform-specific limitations, and return fields. Minor gap: it doesn't clarify that only one platform is queried per call (implied by the single enum parameter).

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%, with per-platform defaults and country constraints already documented in the schema. The description's phrase 'by keyword / by brand or website / by brand name' reinforces but does not extend the schema's parameter documentation, 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?

Names a specific verb and resource ('find ads other brands are running') and enumerates the three supported platforms with their respective search semantics. Clearly distinct from siblings like search, search_vault, and list_viral_youtube_videos.

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?

Gives plan gating ('Amanah, Iltizam and Ihsan plans only'), cost ('No credits used'), and a concrete usage scenario ('good for ad ideas before making pictures with place_product or generate_image'). It stops short of an explicit exclusion versus the general-purpose search sibling.

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