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

Annotations give destructiveHint=true, but the description adds genuinely useful context the annotation cannot: that this is purely a record-creation step that "MOVES NO MONEY" and carries "no bank details." That runtime/scope framing is valuable for an agent reasoning about financial risk. It stops short of describing return values or idempotency, so it is not a 5.

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 short, front-loaded sentences with zero filler. The most important facts (what it does, what it does not do, the underlying endpoint) come first and each sentence earns its 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 3-param create tool with one required field, no output schema, and full schema coverage, the description covers purpose, scope, and endpoint adequately. Minor gaps remain: no statement of return shape (the created record id) or what happens on duplicate/invalid input, which an agent calling it would benefit from.

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 schema already documents all three parameters (name, email, metadata); baseline 3 applies. The description adds no format, validation, or constraint detail beyond what the schema provides.

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?

Specific verb+resource ("Creates a counterparty (contact) record in Modern Treasury") and it disambiguates from the read-only siblings (get_counterparty, list_counterparties) by being an explicit create. The parenthetical "(contact)" further pins down what a counterparty is. No ambiguity about what operation this performs.

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?

The scope caveat ("Creates a record only — no bank details, MOVES NO MONEY") implies the tool's role but never states when to use it versus alternatives or prerequisites (e.g., whether it must exist before creating payment orders). No sibling is named or excluded, so usage is only implied.

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