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

Annotations already declare readOnlyHint/idempotentHint, so safety is covered; the description adds genuinely new behavior: per-media-type provider routing and the TVDB→TMDB fallback. It does not cover failure modes or result counts, but an output schema exists. Note: the description's 'EXTERNAL databases' framing sits uneasily with openWorldHint=false — the annotation appears stale rather than the text being wrong, so this is not scored as a contradiction.

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 highest-value distinction (external vs owned) before the provider list. Four short sentences, each doing work, though the closing anime/show sentence is redundant with the 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?

Return values are covered by the output schema, and routing plus alternatives are well explained. One real gap: the media_type enum includes podcast and manga, but neither appears in the data-sources list, so an agent gets no signal about where those are resolved.

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 each of the four parameters is documented in the schema, so baseline 3 applies. The description's only added parameter guidance ('use anime not show') is already duplicated verbatim in the media_type schema description, so it adds no new meaning.

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+resource (search external databases to find items) with an explicit scope contrast: external sources, NOT the user's collection. It then enumerates the exact provider per media type (OpenLibrary, TMDB, TVDB, Discogs, AniList, IGDB), which makes it unmistakable versus siblings like search and get_details.

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 explicit timing ('BEFORE adding them') and names the alternative for the opposite case ('Use search/get_details for items the user already owns'). It also resolves the one enum ambiguity that would cause a miscall: anime vs show for Japanese animation.

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