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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses that the tool may perform up to 3 cold fetches and that legacy KR add-on accounts are charged a daily research credit even on cache hits. This is substantive behavioral and cost transparency 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?

Two tight sentences front-load the core purpose, then add the most decision-relevant behavioral details (project_id conditional behavior and cost). There is no filler or repetition of schema boilerplate.

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?

Given the readOnlyHint/openWorldHint annotations, an output schema, and the optional project_id behavior, the description covers what an agent needs to invoke it correctly: scope, outputs, conditional behavior, and cost implications. No critical operational detail 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?

The description repeats and reinforces project_id's role (overlay winnability, empty recommendations without it), but the schema already documents that. language_code and location_code are left unexplained in both the description and schema, so at 50% schema coverage the description only partially compensates for the gap.

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 opens with a specific verb and resource ('Analyze a competitor domain') and immediately lists concrete outputs: organic/paid footprint, estimated traffic and traffic value, position split, and top-ranking keywords. This makes the tool's purpose distinct from siblings like get_backlink_profile or research_keywords without needing to open the 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?

It gives clear conditional guidance: pass project_id to enable winnability overlay and recommendations, omit it to get empty recommendations. It also warns about credit costs. It does not explicitly name when to prefer an alternative sibling, but the context is otherwise actionable.

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