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

With no annotations, the description carries the full burden and largely meets it: it discloses that the data is 'the tracked view, built from what we have recorded' (i.e., recorded snapshot data, not a live fetch), states the account requirement, and names the exact recovery path (signup URL, reconnect via the URL on /profile). It does not explicitly state that the call is non-mutating or describe freshness/pagination limits, leaving a small 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?

Four short paragraphs, each with a distinct job: what it returns, return shape, alternatives for time series, and access/fallback. The purpose is front-loaded in the first clause. The account/signup paragraph is the most verbose part but is genuinely load-bearing for a gated tool.

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?

No output schema exists, so the description must explain the payload, and it does: per-store-listing latest numbers, tracked keywords with positions, and a 'locales' field with per-language keyword counts. Combined with the access-path detail, an agent has enough to invoke it correctly; only return-format specifics (field names, pagination) are absent.

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% and the single parameter is documented in the schema as 'From list_extensions.' The description adds no syntax or provenance detail for extension_id, but it does explain the returned 'locales' structure, which is output rather than parameter guidance. Baseline 3 when the schema does the work.

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+resource ('One extension in full') and enumerates contents: every store listing's latest numbers, tracked keywords, and their current positions. It explicitly contrasts itself with get_store_listing ('the tracked view ... For an extension this account does not track ... use get_store_listing instead'), so an agent can distinguish it from siblings without opening a 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?

Gives explicit when/when-not routing: use get_metrics_history or get_keyword_ranks for movement over time, and get_store_listing for untracked extensions or listings in other languages. It also states access prerequisites (ExtensionDash account) and names the fallback tools that still work without one.

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