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

readOnlyHint=true already tells the agent this is a safe read, and the endpoint mapping (GET /rinv/{hash_key}) reinforces that it is a non-mutating fetch. However, nothing is said about error behavior for an unknown hash_key, permissions, or what the returned profile contains, so it adds little beyond the annotation.

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 key requirement front-loaded; nothing is buried. The REST endpoint fragment is mildly redundant with the tool name but still provides a useful mapping for an agent crossing MCP and API docs.

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 one-parameter read tool with readOnlyHint and no output schema, the description is minimally sufficient to call correctly. It does not describe the shape of the returned recurring invoice profile (fields, line items, schedule) even though no output schema carries that burden.

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% and the schema itself already clarifies that hash_key is a short string rather than a numeric id. The description only restates "by hash_key" and adds no format guidance beyond the schema, so baseline 3 applies.

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 and resource ("Get one recurring invoice profile") and scopes it to a single record via hash_key, which distinguishes it from hiveage_list_recurring_invoices. It never names that sibling explicitly, but the singular/by-key framing makes the distinction inferable.

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?

Usage is only implied: the agent can infer this is the lookup-by-key path when it already holds a hash_key. No explicit when-to-use or when-not guidance, and no mention of sibling tools like list_recurring_invoices or list_connection_recurring_invoices as alternatives.

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