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

Annotations already declare non-readOnly, non-idempotent, non-destructive, closed-world. The description adds genuinely useful behavioral context the annotations cannot: the override persists across subsequent Plaid syncs and self-clears when Plaid reports a refreshed balance. This lifecycle detail is valuable, though auth/permission requirements and error behavior are unstated.

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?

Front-loaded with the core purpose followed by the trigger and lifecycle, which is good ordering. The Args/Returns blocks partly restate the schema shape, but since the schema has no descriptions they earn their place.

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 2-param mutation with no output schema, the description covers purpose, trigger, constraint, lifecycle, and return shape (updated snapshot with balance_status). Nothing an agent needs to invoke it correctly is missing.

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 0%, so the description carries the param burden. It clarifies account_id must reference a Plaid-linked account and that new_balance accepts negatives for overdraft or credit balances exceeding the limit, which meaningfully extends the bare integer/number schema.

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 verb (override) plus resource (Plaid-linked account's balance) and contrasts with the adjacent concept of a manual account whose balance is edited directly. An agent can distinguish this from update_account or accept_plaid_balance from the text alone.

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?

Explicitly states when to use it (Plaid reports a stale or incorrect balance from a mismatched feed or delayed clearing) and when not to (manual accounts, which are edited on the account itself). The triggering condition and the excluded alternative are both named.

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