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

The description goes well beyond annotations by disclosing idempotent-like behavior ('Already-present creators are reported, not duplicated'), unresolved creator handling ('unresolved ones come back in notFound'), allowance consumption, and over-limit behavior. This is rich behavioral context that annotations alone do not provide.

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 is front-loaded with the primary action and packs many important details into a compact paragraph. The only minor redundancy is stating 'Free to call' and 'Cost: free' separately, which is slightly repetitive but not distracting.

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 tool with no output schema, the description covers key invocation details: input formats, limits, prerequisites, failure behavior for unresolved IDs, non-duplication, and allowance consequences. It is complete enough for an agent to select and call the tool correctly, though exact success response shape is not described.

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 meaningful context beyond the schema by explaining where profileIds come from ('from search_profiles or any search result'), clarifying the shape of handles as {platform, handle} pairs, and reinforcing the 25-per-call limit. This pushes it above baseline.

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 clearly states the action ('Adds creators to one of your watchlists') and identifies the key resource (watchlists and creators). It distinguishes itself from siblings like remove_watchlist_profiles through its explicit add semantics and covers both input modes (profileIds and handles).

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?

The description provides clear context on when to use the tool, including the prerequisite that creators must already be tracked and the explicit instruction to 'crawl_profile first if not'. It does not explicitly name alternatives for removing creators, but the usage context for adding is well specified, so only minor exclusion guidance is missing.

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