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

Annotations cover safety (readOnly, idempotent, non-destructive), and the description adds substantial behavior beyond them: plan-locked fields return null and are named in `locked`, `lockedCount` semantics, an instruction never to estimate locked data, that results are not shown until sightglass_show is called with resultId, and that no account is required. This is rare, high-value disclosure.

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?

Front-loaded with the core purpose and competitor scope, then workflow and plan caveats. Dense and mostly earning its place, though the show/resultId and auth instructions make it longer than strictly necessary for a single read tool.

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?

No output schema exists, and the description compensates fully: it enumerates what comes back (category breadcrumb, Meta pages, grade mix, Momentum components) and explains the locked/lockedCount plan-gating and the show-vs-fetch split. An agent has everything needed to call and interpret it.

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 schema already documents all three params. The description still adds semantic sourcing for companyRef (from search_companies or an ad's advertiser), which goes beyond the schema's brief 'Company id or slug.' projectId/workspaceId are left to 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 resource and scope — 'One company's full profile plus its six nearest competitors' — and enumerates the returned contents, making it clearly distinct from sibling sightglass_search_companies and sightglass_get_company_activity.

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?

Explicitly tells the agent where the reference comes from (id/slug from sightglass_search_companies or the companySlug on an ad's advertiser) and routes trend/launch history to sightglass_get_company_activity. 'Works without a Replo account: call it before asking the user to sign in' is a concrete when-to-use rule.

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