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

Annotations already cover the safe-read profile (readOnly, idempotent, non-destructive), and the description adds substantial behavior beyond them: results are data only and nothing renders until sightglass_show, locked plan-gated fields return null and are named in `locked`, `lockedCount` signals what a higher plan reveals, and the agent is told never to estimate locked data. This is exactly the extra context annotations cannot carry.

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 purpose and scope are front-loaded, and despite its length most sentences carry distinct load-bearing information (axes semantics, plan locking, show routing). A few clauses restate schema content (kind values) and the map framing is mildly redundant, so it is dense but slightly over-full.

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 tool with no output schema, the description fully characterizes the return shape: a 0-100 position per axis, raw similarity, locked/lockedCount, and isYou marking, plus the two-step show workflow. Nothing material to calling it correctly is missing.

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, but the description adds meaning: a worked custom-axis example ([{low:'Minimal', high:'Maximal'}]), the rule that omitting `high` auto-names the opposite, and that the user's own company/Brand Studio personas are always included and marked isYou. The explicit lens preset pairs also reinforce the enum beyond the schema's terse mapping.

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 and resource: placing personas, ads, landing pages or companies onto 'this vs that' axes on the Sightglass Arena map. It situates itself clearly against siblings by naming the map UI and the sightglass_show follow-up, so an agent can tell what it does without opening the 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 concrete triggering questions ('where do we sit against these brands', 'which buyers are nobody's focus') and explicit lens-vs-custom-axes guidance, plus the crucial routing rule to call sightglass_show with resultId afterward. It lacks an explicit 'when not to use' or contrast against search/research siblings like sightglass_xray or sightglass_get_rankings.

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