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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered; the description goes beyond them by disclosing the error envelope (single-element list with api_error/task_error/dfs_timeout/dfs_unreachable) and instructing a pre-check for 'error'. That is exactly the kind of failure-mode context structured fields do not carry. It does not state rate limits, cost, or freshness of the SEO data, so it is not exhaustive.

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-loaded with the core semantics and then terse per-topic lines (location/language, errors, workspace) with no filler. The dense German telegraphic style packs a lot into few words, though the mid-sentence error-tuple enumeration slows reading slightly.

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?

An output schema exists, so return-value explanation is not required, and the description still adds the practically important failure shape. With 5 optional-ish parameters and only the limit left unaddressed, an agent has enough to call this correctly; covering limit's effect on result count would close the remaining gap.

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 description coverage is 0%, so the description bears the full burden: it explains workspace (optional when only one workspace) and that location/language default from the workspace with the same format as dfs_keyword_volume. However, 'limit' (default 50) is never mentioned, and the location/language format is deferred to another tool's documentation rather than stated, leaving gaps for a 5-parameter tool.

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 result set (long-tail keyword suggestions containing the seed as a substring) and immediately differentiates from the closest sibling by noting it is broader than dfs_related_keywords. An agent can distinguish this from the other dfs_keyword_* tools without opening a 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?

The parenthetical 'breiter als dfs_related_keywords' gives a concrete selection criterion against the nearest alternative, and the error-checking instruction tells the caller how to handle results. It stops short of naming the case where the narrower sibling is preferred, so the routing guidance is directional rather than bilateral.

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