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

Goes well beyond the annotations: discloses the destructive list-replacement semantics (partial lists wipe existing values), warns that editing a live ad triggers Microsoft review, states the return value (previous text, so it can be restored), and explains dryRun is free and cannot affect spend. This is exactly the mutation-risk context annotations alone (destructiveHint/idempotentHint) cannot convey.

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?

Four short sentences, front-loaded with what changes, then the replacement caveat, then the review consequence, then the dryRun recommendation. Every sentence carries distinct operational information with no filler.

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 9-parameter mutation tool with no output schema, the description covers the mutation risk, the review side-effect, the return payload, and the safe-preview path. An agent has everything needed to invoke it responsibly.

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 coverage is 100%, so the baseline is 3, and the description earns a bump by clarifying the non-obvious semantics of 'headlines'/'descriptions' as whole-list replacement rather than merge, plus steering to dryRun. It adds no character limits or counts, but those are already in the schema.

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 (Change) and resource (responsive search ad) and enumerates the editable fields: headlines, descriptions, final URL, display paths. This cleanly separates it from msads_create_responsive_search_ad and from status-only siblings like update_ad_status, without the agent needing to open another 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?

Gives explicit operating guidance: use dryRun first, and send the complete new set when passing lists. It does not spell out when to prefer a sibling tool (e.g. update_ad_status for pausing), but the field list implicitly excludes those cases and the dryRun-first instruction is a concrete usage rule.

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