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

Annotations cover the write/safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds real behavioral context beyond them: the multi-step external pipeline, non-duplication on re-run, and honest fallback when prerequisites are absent. The claim that it 'updates the existing set rather than duplicating it' sits in mild tension with idempotentHint=false, though this is not a flat contradiction.

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?

Three sentences, front-loaded with the core action and pipeline, followed by re-run guidance and edge-case behavior. Dense and purposeful; no filler or restated name/title noise.

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?

Despite no output schema, the description explains what is returned in normal and degraded cases ('gets back its existing set... and an honest reason instead of a new one'), which is exactly the return-value information an agent needs. Combined with the annotated safety profile, nothing material is missing for correct invocation.

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?

Only one parameter (brandId) and the schema already documents it fully (100% coverage, including the 'from list_brands' provenance). The description references 'this brand' but adds no format, constraint, or sourcing detail beyond the schema, so the baseline of 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?

The description names a specific verb+resource ('Finds or refreshes this brand's competitor set') and lays out the exact pipeline (site research → Google Places search → Instagram/Facebook handle resolution → scoring). It is clearly distinguishable from the sibling list_competitors, which is the read-only counterpart. An agent can tell what this does without opening any 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?

It gives explicit when/when-not guidance ('Meant to be re-run occasionally, not on every call') and discloses the non-duplicating re-run behavior, plus two failure modes (no site research, national/online brand) with the resulting fallback. It stops short of naming list_competitors as the alternative for simply viewing the set, so the routing is implied rather than stated.

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