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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, yet the description still adds real behavioral context: one point per real scheduled check, oldest-first ordering, empty-until-populated, and explicitly never interpolated or back-filled. That directly answers what the returned series does and does not contain.

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?

Purpose is front-loaded in the first clause, with supporting semantics (ordering, emptiness, no back-fill) and the cost note following in tight, non-repetitive sentences. No sentence is wasted.

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 read-only trend tool with no output schema, the description does useful work by naming the fields in each point, its ordering, and its emptiness/gap behavior, which compensates for the missing return schema. Minor gap: it doesn't state pagination or point-count limits for long histories.

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%, so both required params (projectId, trackedPromptId) are already documented with sourcing hints (list_projects, list_tracked_prompts). The description adds no parameter-level detail, so baseline 3 applies; the mentionedByCount/citedByCount fields it cites are outputs, not inputs.

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: observed history for one tracked prompt, one point per scheduled check. It is distinguishable from sibling trend tools (get_brand_scan_trend, get_rank_ai_overview_trend) by scoping to a tracked prompt, though it never names an alternative explicitly, so sibling differentiation is only implicit.

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?

Usage is implied rather than stated — the agent can infer this returns a time series once checks accumulate, and the 'empty until checks accumulate' note warns against expecting data. But it never says when to reach for this versus list_tracked_prompts or the other trend endpoints, and gives no exclusions.

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