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

The description explicitly says 'MUTATES', clearly disclosing that this is a write operation. It also reveals an important side effect: changing criteria replaces the definition and clears pending hits, with the next daily evaluation repopulating them. This goes well beyond the annotations, which only indicate readOnlyHint=false and destructiveHint=false.

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 compact and every sentence earns its place. It front-loads the core action and mutation warning, then adds side-effect, tuning, and authentication guidance without unnecessary verbosity.

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 this complexity—nested criteria, multiple update targets, mutual address options—the description covers the essential operational context: mutation, side effects, default ranking behavior, the preview_watch alternative, and the required API key. The output schema reduces the need to explain return values, and the tool is well-scoped for an agent to invoke 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, but the description adds meaningful parameter context: it explains that criteria is a full replacement, that changing it clears pending hits, that 'rising' is the default rank, and that min_impact_pct creates an anti-noise watch. This adds value beyond the raw schema definitions.

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 specific action: updating an existing watch in place, and enumerates what can be updated: rename, novelty_min, or criteria. It also distinguishes itself by mentioning the structured filter retargeting and the address-by-watch_id-or-name, which separates it from create_watch and delete_watch.

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 gives a clear usage context: when you need to modify an already-created watch. It also directs the agent to preview_watch first when tuning criteria, which is a helpful alternative. It does not explicitly spell out when not to use the tool or compare with create_watch/delete_watch, so it stops short of a 5.

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