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

Annotations only declare readOnlyHint=false and destructiveHint=false, but the description discloses far more: activation is blocked if the config isn't ASC-606-conformant, cadence/validity values must satisfy the type's contract, direction and type are posting-locked once a document hits the ERP. Most importantly it discloses the non-obvious side effect that a validity change raises a gated Recalculate card rather than posting money, and nothing is backdated without operator approval.

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 and editable field list are front-loaded, followed by constraints and then sibling routing — a sound order. The constraint sentence is dense and clause-chained with four semicolon-separated rules, and the direction semantics are restated in both description and schema, shaving off the top score.

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 an eight-parameter, governed financial mutation with no output schema and only generic annotations, the description covers prerequisite access, contract validation, posting locks, approval gating of downstream recalculation, and alternative tools for adjacent operations. An agent has everything needed to call it correctly and predict its side effects.

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 all eight parameters are already documented, including the enum for direction and the null-for-open-ended convention on valid_to. The description adds one genuinely new piece of meaning — patch semantics, "send only the fields to change" — but otherwise restates the schema's field meanings rather than extending them, so the baseline 3 holds.

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?

A precise verb plus resource ("Change an agreement's TERMS") immediately followed by the exact set of editable fields: name, counterparty, direction, validity window, cadence. It also explicitly names what this tool is NOT (rates, status), so the agent can distinguish it from edit_agreement_rates and close_agreement without opening any 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 gives an explicit routing rule — "To CHANGE RATES use edit_agreement_rates; to change STATUS use the audited status flow" — plus the calling convention "Send only the fields to change." The precondition (agreement_id required, connected Aurgus account) is stated, leaving nothing to inference.

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