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

Goes well beyond the annotations (which only declare idempotent/non-destructive). It discloses that the call is free, that re-saving is a no-op, that missing tags may be created and appended rather than replaced, and that saving does not fetch metrics (null volume/difficulty/CPC). This is exactly the extra behavioral context an agent needs.

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-loads the core purpose and cost, then layers behavior (idempotency, tags, dedup, metrics) in compact sentences. Despite being several sentences, every one carries distinct, non-redundant information that an agent needs.

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 5-param mutation tool with no output schema, the description is complete: it covers cost, idempotency, tag side effects, the savedCount return semantic, and the metrics gap. Defaults for languageCode/locationCode are handled by the schema, so nothing essential is missing.

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 baseline is 3, but the description adds genuine meaning beyond the schema: it explains tag append-vs-replace behavior, and clarifies that savedCount reflects DISTINCT normalized/de-duplicated keywords rather than entries submitted, which directly disambiguates the 'keywords' parameter semantics.

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+resource in the first sentence: 'Save keywords to a project's saved-keywords list.' It clearly distinguishes itself from siblings like list_saved_keywords and research_keywords by describing the write-to-saved-list operation, and the metric caveat further separates it from research_keywords.

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?

Provides clear context: free/credit-free saves, ask user confirmation before applying or replacing tags broadly, and an implicit when-not signal via 'until research_keywords has run for it' for metric data. It stops short of explicitly naming alternatives for keyword-research workflows, but the conditions are clear.

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