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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful behavior beyond that: mal=true triggers one extra fetch scraped credential-free from the public MAL page, and is omitted when there is no MAL id. It stops short of mentioning rate limits or failure modes, but the enrichment cost and data provenance are disclosed.

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 purpose and then the optional enrichment, with a clear routing sentence at the end. The long enumeration of normalized fields is dense and partly overlaps the output schema, so it is informative but not maximally tight.

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?

An output schema exists, so return values need not be spelled out, yet the description still lists them (partly redundant). For a 2-parameter read-only lookup it gives the agent enough: what it returns, the mal enrichment behavior, credential-free provenance, and the sibling to use for searching.

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 id and mal parameters are already documented, setting the baseline at 3. The description adds the shape of the resulting mal block (0-10 score plus scored-by count) and the fetch/no-MAL-id edge case, slightly exceeding the schema's description of the parameter's effect.

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 ('Returns') and resource ('a normalized anime by AniList id'), then enumerates the normalized data fields. It also names the sibling anime_search and its differing use case, so an agent can distinguish this lookup tool from the search tool without reading either 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?

The final sentence explicitly routes search-style needs to anime_search, giving a clear when-not-to-use signal. However it never states the trigger condition for using this tool beyond the implicit 'you already have an AniList id', so it stops just short of full explicit when/when-not guidance.

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