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

Annotations already declare readOnly, idempotent, and non-destructive, and the description adds substantial behavior beyond them: equivalent URLs return the same answer (URL normalization/determinism), 'zero yanks is an answer, not an error' (empty-result semantics), 'for up to five yanks' (truncation cap), and 'never fetches the source' (side-effect guarantee). No contradiction with annotations.

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?

Four sentences, each earning its place and front-loaded in order: purpose, parameter semantics, return format/empty semantics, and safety guarantee. The parenthetical URL-form list is long, but it justifies its length by making the hard-to-guess normalization behavior concrete.

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 must carry the return contract, and it does: real counts (yanks, lines, verbatim lines) plus per-line details for up to five yanks. It also covers empty-result semantics, the truncation cap, and the no-fetch safety guarantee, leaving nothing missing for a single-parameter, read-only tool.

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%, but the description converts the schema's generic 'in any of its forms' into actionable specifics: youtu.be timestamp short links, playlist watch URLs, tracking-parameter-laden articles, Apple Podcasts/Overcast episodes. It also attaches the normalization guarantee to the sole parameter, materially enriching the single url field.

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?

Opens with the directive 'Ask before you extract' and names the resource precisely: 'everything yank.info already holds from one source URL.' The breakdown of return values (counts, lines, verbatim flags, timestamps, moment links, card URLs) makes the scope concrete, and the strict one-URL focus differentiates it from the search/quote siblings without needing to name them.

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?

'Ask before you extract' frames the tool as a pre-extraction lookup, giving clear workflow context for when it should be called first. However, no sibling tool is mentioned, so there is no explicit when-not-to-use routing; the boundary versus search_lines and get_yank must be inferred from the 'one source URL' vs. query/ID framing.

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