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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds real value beyond that: it discloses the result shape (id, description, scheduled time, recipient counts), the pagination mechanism, and that total_count reports the full population.

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 clauses, with the resource definition front-loaded before the paging advice and the return-count note. The trailing 'GET /message/scheduled' is mildly redundant for an MCP caller but not wasteful enough to hurt.

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?

With no output schema, the description usefully names the returned fields and total_count, and the fully documented input schema covers the parameters. The only material gap is that it never says scheduled messages disappear from this list after sending, which affects interpretation of results.

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 each of the three parameters is already fully documented in the schema, including the order enum. The description echoes offset and limit but adds no syntax or default detail beyond them, and omits order entirely — baseline 3 is correct.

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 resource with a scoping qualifier — 'Messages that are scheduled and not yet sent' — and enumerates the returned fields, so an agent can distinguish it from get_message and cancel_scheduled_message. It stops short of explicitly naming a sibling, but the verb+resource+scope is unambiguous.

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 implied rather than stated: 'Use offset and limit to page' tells the agent how to consume results, but there is no guidance on when to prefer this over get_message or other list tools, nor any prerequisite/conclusion, as messages leave the list once sent.

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