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

With no annotations, the description carries the full disclosure burden. It usefully adds the finance:write scope requirement and the side effect that a category is auto-applied when matchSource="rule" and the subscription has a categoryId, but it stays silent on mutation semantics (whether existing links are replaced, idempotency, partial-failure behavior).

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?

Three sentences, each load-bearing: purpose first, then matchSource behavior, then the auth prerequisite. No redundancy with the schema, no filler.

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 3-parameter mutation with 100% schema coverage and no output schema, the description covers purpose, the key conditional side effect, and the required scope. It is nearly complete, only missing link-replacement/idempotency behavior.

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%, so the baseline is 3. The description goes beyond the schema's enum listing by explaining the functional consequence of manual vs rule values, adding real meaning the schema does not convey.

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?

"Link one or more transactions to a subscription to mark them as payment instances" gives a specific verb, resource, and the resulting business effect, so an agent can distinguish it from the inverse sibling unlink_transactions_from_subscription 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 states when to use matchSource="manual" (user-initiated linking) and explains the rule-driven branch, which guides selection among matchSource values. It does not, however, name the undo path or exclusion cases for when not to use this tool.

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