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

Annotations cover the safety profile, and the description adds substantial behavior beyond them: plan-gated fields return null and are named in each item's `locked` list, `estimates` maps to sales/visits/traffic, `lockedCount` indicates how many more results a higher plan yields, the agent must say data is on a higher plan and never estimate it, and the tool returns data only with nothing shown until sightglass_show is called.

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?

It is long but front-loads the core concept and every clause carries information (field inventory, sort order, plan-locking, show workflow). The single dense paragraph is heavy to parse, keeping it from a 5.

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?

There is no output schema, so the description carries the return-value burden and does so by enumerating angle fields, counts, dates, offers, and the locked/estimates mechanism. It also covers the required handoff to sightglass_show, leaving nothing essential unspecified.

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 companyRef, projectId and workspaceId are already fully documented in the schema. The description adds no parameter-level syntax or format detail beyond that, so the baseline 3 applies.

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 gives a concrete verb+resource and defines what an 'angle' is in domain terms (the pitch each ad leans on, with type, name, hook, persona, offers), which clearly separates it from offers or personas. It stops short of naming its nearest sibling (sightglass_find_top_angles) to draw the boundary explicitly.

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 states the intended questions ('how does this brand sell', comparing two brands' messaging) and gives an explicit follow-up rule: call sightglass_show once with this call's resultId, which does not re-search. No when-not-to-use or alternative-tool guidance, so it falls short of a 5.

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