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

With annotations already covering readOnlyHint, idempotentHint, and destructiveHint, the description adds substantive behavioral context: it returns only summary rows, returns an empty list when there is no linkGroup, and returns 404 for unknown or unowned characters. This ownership/error behavior goes beyond the annotations and does not contradict them.

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?

The purpose is front-loaded in the first sentence, and the description is compact—covering output shape, follow-up workflow, and error/edge cases in three sentences. The field enumeration overlaps somewhat with the declared output schema, but the overall structure is scannable and free of unrelated detail.

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 single-parameter read-only list tool, the description covers the purpose, ownership precondition, output semantics, empty-list edge case, error behavior, and the appropriate next tool for full details. Combined with the annotations and output schema, an agent has everything needed to call the tool correctly.

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?

The schema already describes the single `id` parameter as the Mongo _id of an owned character, so the baseline is 3. The description adds meaningful nuance by clarifying that this id refers to the source character and that the result contains every OTHER sheet in its linkGroup, meaning the input character itself is excluded from the output.

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?

The description opens with a precise action and resource: 'List the linked sibling sheets of a character the user owns — every OTHER sheet in its linkGroup.' It clearly distinguishes itself from vault_get_character by stating it returns summary rows rather than full sheets, and it explicitly excludes the input character from the result set.

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 description gives clear context for when to use the tool: pass an owned character id and get its linked sibling sheets. It also names the explicit alternative follow-up, 'follow with vault_get_character on a returned id for a full sheet,' which tells the agent when to switch to the full-sheet tool, and it documents edge cases (empty list, 404).

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