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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true and idempotentHint=false, so the safety profile is covered structurally. The description adds the scoping behavior (site_id narrows to one brand, omission returns account-wide), which is genuinely useful, but says nothing about result format, pagination interplay, or ordering.

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 short sentences, zero filler, and the scoping constraint is front-loaded immediately after the purpose statement.

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 zero-required-parameter read-only list tool with a fully documented schema and clear annotations, the description covers what the tool returns at a high level. It does not mention pagination or default result count, but with the limit parameter documented in schema and no output schema to reconcile, this is a minor 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 100% and both parameters (limit, site_id) are documented in the schema itself. The description's site_id note largely restates the schema text ('Omit for every session on the account'), and limit is not mentioned at all, so no meaning is added beyond the structured fields.

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 and resource: 'List keyword research sessions.' An agent can distinguish it from create_keyword_session / delete_keyword_session / get_keyword_session by the verb alone, though the description never explicitly names those alternatives.

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 one usage rule ('Pass site_id to see only that brand's sessions'), which covers the filtering case, but says nothing about when to use this list tool versus get_keyword_session for a single session or how the account-level default relates to siblings.

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