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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, so the safety profile is covered. The description usefully surfaces the mandatory confirmation gate that must be set before execution, but it says nothing about partial-update semantics — critically, whether omitted fields (amount, category_id, date, notes) are preserved or cleared — nor about reversibility or audit effects for a destructive mutation.

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?

Two short sentences with the core action first and the execution prerequisite second — nothing is padded or buried. The terseness is close to under-specification rather than bloat, but structurally it is efficient and front-loaded.

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 destructive mutation with no output schema and 25% schema coverage, the description leaves far too much implicit: partial-update behavior, required permissions, what the response contains, and the meaning of most parameters. The confirmation note is a good start but does not carry the burden the thin schema and annotations place on it.

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 only 25%: of eight parameters, only confirmation and idempotencyKey carry descriptions, and the description text merely echoes the confirmation rule already stated in the schema. Six parameters (date, notes, amount, category_id, description, transaction_id) are undocumented in both places, including whether transaction_id identifies the record and whether nulls clear values.

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?

"Update an existing transaction" names the verb and resource, but it is essentially a restatement of the tool name and title, adding only the word "existing." It does not distinguish the tool's scope from siblings like add_transaction, delete_transaction, or bulk_add_transactions beyond what the name already implies.

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?

There is no guidance on when to reach for this tool versus add_transaction (for new records), delete_transaction (for removal), or get_transaction/list_transactions (for reads). The only usage-adjacent statement is the confirmation requirement, which is a gate rather than a routing rule.

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