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

With no annotations, the description carries the full behavioral burden and does so: it discloses the 3-credit cost, the row cap semantics (a full-page response is capped, not complete), the absence of offset/paging and the billing reason behind it, and the recommended remedy of a single larger call. This is unusually rich disclosure for a billed read tool.

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-loaded with purpose and output, then routing, then cost, then the cap caveat. Every sentence earns its place, though the cap/paging explanation is dense and could be tightened without losing meaning.

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 convey return content, and it names the exact fields (search volume, difficulty, their position, estimated traffic). Combined with the cost, cap, and input-routing guidance, an agent has everything needed to call it correctly.

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%, so the baseline is 3. The description adds meaning beyond the schema by explaining the site_id/your_domain relationship (site_id auto-resolves your domain; otherwise pass your_domain) and by tying the row-count advice to the limit parameter, which the schema documents only as a max.

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 ('Find what a competitor ranks for that you don't') and specifies the exact output set ('every keyword where they appear and you do not appear at all'). It distinguishes itself from siblings by contrasting with Search Console's own-property limitation and referencing SERP_Snapshot as a source of competitor domains.

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 how to select the competitor (one you know you compete with, or a repeat domain from SERP_Snapshot), how to identify your own site (site_id vs your_domain), and why Search Console cannot substitute. The when-to-use conditions and the alternative source are all spelled out.

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