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

With no annotations, the description must carry the behavioral burden, and it does disclose return structure (nested chapters/episodes in order). It says nothing about what happens for an unknown id, whether the response is filtered by locale, or the read-only nature of the call – all inferable but not stated.

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?

A single economical sentence with no wasted words, and the key fact (arc plus ordered chapters/episodes) is front-loaded. It is grammatically a fragment rather than a full statement, which slightly reduces clarity without adding noise.

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?

For a simple two-parameter read tool with no output schema, the description gives a partial picture of the return shape (ordered chapters and episodes) but omits other likely fields. Adequate but not complete enough to predict the payload.

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%, and both parameters are well documented there, including the locale enum and the note that non-ja locales only include translated episodes. The description adds no meaning beyond that, so the baseline 3 applies.

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 ('One story arc') and what comes back with it ('its chapters and episodes in order'), which distinguishes it from the sibling list_arcs by being singular and scoped to one arc. The missing piece is an explicit verb – it reads as a noun phrase, leaving the retrieval action implied by the name get_arc.

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?

No guidance on when to select this over get_episode, get_character, or list_arcs; the only routing hint ('Arc id from list_arcs') lives in the schema, not the description. An agent must infer from the name alone that this is the follow-up to list_arcs.

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