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

Annotations only carry the generic readOnly/destructive/idempotent/openWorld flags, but the description adds substantial behavior: which fields are copied vs. left ruleset-local, the cascade-on-edit semantics, campaign-leg replication, and concrete 403/404/409 failure modes. This is far more than the annotations convey.

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 core action is front-loaded in the first clause, and every sentence carries information (copy manifest, cascade, campaign legs, error codes, sibling contrast). It is dense and long for a single paragraph, which slightly reduces scannability.

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 mutation with an output schema and annotations, the description covers the source/output construct, field-copy rules, cascade behavior, campaign replication, and error responses. An agent has everything needed to invoke it correctly and interpret failures.

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 already 100%, so the baseline is 3, but the description adds meaning beyond the schema: the one-sheet-per-ruleset-per-group rule and the 409 conflict when the source is already that ruleset or a sibling occupies it. It does not elaborate on the `id` parameter, keeping it from a 5.

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 states a precise verb and resource ('Create a linked sibling sheet for a character the user owns, in a different ruleset') and immediately explains what a 'linked' sheet is (same persona, shared linkGroup). It explicitly contrasts itself with the sibling vault_clone_character, so an agent can disambiguate without opening 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?

It names the alternative tool and the exact selection condition: 'This is NOT vault_clone_character — clone deep-copies the whole ruleset-specific sheet; spawn deliberately does not.' It also states the preconditions (user-owned source, different ruleset, entitlement for restricted rulesets) that gate legitimate use.

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