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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely new context beyond that: it discloses the shape of the return value (each product with a one-or-two-sentence description) and the slug semantics that link this output to submit_campaign_brief. It says nothing about ordering or caching, but for a small fixed catalog that is minor.

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, front-loaded with what the tool returns and followed by the two highest-value facts: where the slugs are consumed and which sibling to prefer for detail. The channel enumeration is slightly long but earns its place by signaling coverage breadth; there is 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?

With no output schema, no parameters, and annotations covering safety, the description is close to sufficient: it describes the entries returned, the slug field's meaning, and routes detail lookups to get_channel. Only minor gaps remain (exact output structure beyond slug/description, ordering), which are low-stakes for a fixed catalog.

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?

Zero parameters, so per the baseline this is a 4. The description correctly spends no words on parameters and instead uses the space to explain the output fields (slug + description), which is the more useful information for a no-arg list tool.

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 conveys a specific resource — the catalog of paid media channels, enumerated (Meta, CTV, mobile, search, audio, OOH) — and makes clear each entry carries a short description and a slug. The listing action is implied by the name rather than stated as a verb, but an agent can immediately tell what comes back and how it differs from get_channel.

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 slugs are what submit_campaign_brief takes as channels' states the downstream use case explicitly, and 'Use get_channel for the full detail of one' names the alternative with the condition that selects it. Both when-to-use and when-to-use-something-else are covered.

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