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

Annotations already declare the full safety profile (readOnly, idempotent, openWorld, non-destructive), so the bar is lower. The description adds value by specifying that the data is a live snapshot at request time plus a trailing 12-month series, and the pricing block discloses billing behavior; it does not, however, discuss rate limits or response shape.

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 two purpose sentences are front-loaded and waste-free, answering what the endpoint returns immediately. The trailing pricing boilerplate and a stray leading formatting character are minor detractions.

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 an output schema present, return values need not be explained in prose, and annotations cover safety; the description adequately conveys what the tool reports and that it needs no inputs. It is essentially complete for a zero-parameter read tool, missing only sibling routing.

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?

The tool takes zero parameters, so schema coverage and parameter-semantics burden are effectively absent; baseline 4 applies. The description correctly implies no input is required ('the moment when you make a request').

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 resource and verb: it returns the total number of backlinks, domains, and pages in the database, plus 12-month stats. This 'index totals' function is conceptually distinct from the target-specific siblings, but the description never names or contrasts any sibling tool, so an agent must infer the distinction.

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?

There is no explicit when-to-use or when-not-to-use guidance and no mention of alternatives among the many get_semrush_* and post_dataforseo_backlinks_* siblings. The intended usage (fetching global index size rather than per-target metrics) is only implied by the purpose sentence.

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