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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safe-read profile is covered. The description adds genuinely behavioral context beyond that: it is non-mutating ('without starting a scan'), it requires a Pro entitlement, and it defines the three degraded outcomes (quiet, no_edition, unknown_niche) an agent must be able to interpret.

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 action and return contents, then prerequisites and status codes. Every sentence carries information, though the final status-code enumeration is packed into a dense single sentence rather than separated, which slightly hurts scannability.

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 takes on the burden of describing returns and does so well, listing the story fields and the sentinel status values. For a two-parameter read tool with full annotation coverage this is close to complete; the only real omission is any note on pagination or edition-count limits.

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 goes beyond the schema by explaining where a valid slug originates (site URL or custom niche URL) and giving additional examples ('founders', 'ai-leaders') not present in the schema's single example. The date parameter's default-latest behavior is restated from the schema rather than extended, so it is not a full 5.

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 ('Read the latest or a dated briefing for a niche') and enumerates the payload (stories, reporting dates, source links, why each story matters, status). It also explicitly separates itself from the scan sibling with 'This reads an existing briefing without starting a scan,' so an agent can route correctly without opening other schemas.

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 input provenance ('a slug from https://nicheangle.com/n or a custom niche's URL, such as founders or ai-leaders'), a default behavior ('latest' unless a date is given), and a precondition ('Assistant access requires Pro'). It stops short of naming niche_signal_scan explicitly as the alternative when the user wants fresh data, so the contrast is implied rather than stated.

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