get_impression_share

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

With no annotations provided, the description carries the full burden. It discloses the core behavior: it shows the percentage of eligible impressions won and distinguishes lost reasons (budget vs. ad rank). This goes beyond the tool name and provides meaningful context about the output's meaning, though it does not cover aspects like data aggregation or authentication requirements.

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?

The description is three sentences, each serving a purpose: the first states what it returns, the second explains the meaning of the metrics, and the third highlights its strategic importance. It is concise, front-loaded, and contains no filler or redundant phrasing.

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 that an output schema exists (so return values are already documented), the description adequately covers the tool's purpose and behavioral nuance. It explains the strategic value and what the metrics indicate. It could be more complete by mentioning how the 'days' parameter affects results or any prerequisites, but for a read-only reporting tool, it is sufficiently complete.

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?

Input schema coverage is 100%, so the baseline is 3. The description does not add any parameter-specific details beyond what the schema already documents (e.g., days, customer_id, login_customer_id). It mentions 'by campaign' which hints at grouping but does not elaborate on parameter semantics.

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 uses a specific verb ('Return') and clearly identifies the resource ('search impression share and lost IS reasons by campaign'). It distinguishes itself from sibling performance tools by focusing on impression share and lost reasons, which is a unique angle compared to tools like get_auction_insights or get_campaign_performance.

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 description implies a use case ('Critical for scaling decisions') but does not explicitly state when to use this tool versus alternatives like get_auction_insights or get_campaign_performance. There is no exclusion criteria or named alternative, so it only provides implied usage context.

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