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

Annotations already declare readOnlyHint and openWorldHint, so the description's added value is the error contract: failures arrive as a one-element list with api_error/task_error, dfs_timeout, dfs_unreachable, and must be checked before evaluation. That is non-obvious behavior an agent would otherwise miss, though rate limits or result ordering are not mentioned.

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 purpose, then mode semantics, then parameter defaults, then the error contract — a sensible ordering with no filler. The telegraphic, parameter-name-first phrasing is dense but each sentence carries information.

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?

With a dedicated output schema, return values need not be described, and the error-shape disclosure plus workspace fallback rules cover the main stumbles for a 7-parameter, open-world read tool. The only real hole is the undocumented `limit` parameter.

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 must carry parameter meaning, and it covers the non-obvious ones: the `intersections` mode switch, workspace defaults for location/language, and the optional workspace slug. It says nothing about `limit` or about expected formats for domain1/domain2, leaving half the surface to inference.

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 the specific operation (keyword overlap of two domains) and even explains the dual mode via `intersections`. It does not contrast itself with nearby siblings such as dfs_competitors_domain or dfs_keyword_ideas_for_domain, so an agent cannot rule those out from the text alone.

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 `intersections=False` gap-mode explanation gives real usage context, and the fallback rules for location/language (workspace default, format as in dfs_keyword_volume) are helpful. However there is no explicit guidance on when to prefer this tool over competing domain/keyword tools, so usage is only implied.

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