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

Beyond the read-only/idempotent annotations, it discloses plan gating with locked fields and lockedCount, that missing-plan fields return null, that the user must be told data is on a higher plan, that output is data-only until sightglass_show is called with resultId, and that show does not re-run the search. This is unusually rich behavioral context.

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 front-loaded with the persona definition and then covers plan gating and the show workflow. It is longer than a minimal definition but most sentences carry practical value; the field inventory is slightly verbose but justified by the absence of an output schema.

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?

With no output schema, the description supplies the return-shape detail (segment nickname, buyer situation, ad share, counts, top angles/offers), the locked-field behavior, and the downstream sightglass_show step. An agent has everything needed to call it and handle the result.

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 the schema already explains companyRef, projectId, and workspaceId. The description adds plan-related context but no parameter-specific syntax or format beyond what is structured, so the baseline of 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 opens with a specific resource — 'A brand's customer personas' — and immediately defines the content: who the brand markets to, age range, awareness stage, angles and offers. This clearly distinguishes it from sibling tools like sightglass_find_angles or sightglass_find_offers.

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 concrete use cases ('answer who is this brand selling to' or compare two brands' audiences) and a key prerequisite ('Empty until the brand has enough ads and pages read'). It does not name alternative tools or state when not to use it, so it stops short of explicit routing.

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