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

With no annotations, the description carries the full burden and does well: it discloses the state machine (PENDING/SENT/REJECTED/FAILED), that tier and tier decision are surfaced, that approval_url appears only while pending, and that a Stripe charge id appears only when billed. It does not mention auth requirements beyond the schema's api_key, rate limits, or read-only/irreversibility guarantees, 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?

A single dense sentence, front-loaded with the verb and the primary status facet, with the secondary facets trailing. Every clause earns its place, though the nested parentheticals make it slightly heavy to parse.

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?

An output schema exists, so the enumerated return fields are partly redundant, but they usefully aid tool selection. The remaining gap is the absence of usage guidance for a polling tool and any note on auth or error behavior; for a 2-required-param read tool this is nearly complete.

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 both parameters are already documented, giving a baseline of 3. The description adds modest context by framing api_key as 'the key's trust tier' and confirming request_id is the send request being queried, but no syntax or format detail beyond the 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 ('Check') and resource ('a send request') and enumerates the exact facets returned: status enum, trust tier decision, approval state, and billing state. The purpose is unambiguous, though it never names the siblings (request_send, draft_letter) or explains how it relates to them, so it stops short of a 5.

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 explicit when-to-use statement, but enumerating PENDING/SENT/REJECTED/FAILED plus an approval_url 'while pending' strongly implies the polling-after-request_send workflow. Usage is inferable rather than stated, which fits a 3.

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