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

With no annotations provided, the description carries the full behavioral burden, and it does well: it explains the sync lag on a fresh link, interprets an empty list (no link, no products, or pending sync), and tells the agent to say which is likely. It also flags case-sensitivity of returned labels. It doesn't describe the return payload shape or pagination, but for a list tool that's a minor gap.

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 description packs purpose, usage guidance, edge-case interpretation, and parameter note into a few efficient sentences, front-loading the main purpose. It is longer than minimal but every sentence earns its place by adding actionable guidance rather than fluff.

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 list tool with 100% schema coverage and no output schema, the description covers the essential context: when to use it, how to interpret results, and the parameter format. The main omission is the exact return structure, but it's reasonably inferable for a label-list tool.

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% — ad_account_id is fully documented in the schema ('Bare 10-digit Google Ads customer ID... No dashes, no act_ prefix'). The description repeats 'ad_account_id is the bare 10-digit customer ID', confirming but not adding meaning beyond the schema, 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 ('List the distinct Merchant Center feed labels') and scopes it to products synced via the Merchant Center link. The description also ties it to the shopping-campaign workflow, which distinguishes it from the many sibling list tools like adsap_google_list_ad_accounts or adsap_google_list_campaigns.

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?

Explicitly says to use it 'before adsap_google_create_shopping_campaign when the user wants to restrict a standard Shopping campaign to one feed' and instructs to pass the returned feed_label exactly as-is. It implies the alternative (omitting feed_label targets all feeds) and names the condition, but does not explicitly name a sibling alternative tool for when you don't need feed labels.

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