Get Messages

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

Adds real behavior beyond the annotations: partial-failure semantics (an unreadable message gets an error entry while the others still come back) and the return envelope { messages, requested, succeeded, failed }, which is valuable since no output schema exists. It does not, however, surface the disk-write side effect of saveAttachments — the one plausible reason the annotations set readOnlyHint=false on a tool described as "Read" — leaving that tension unexplained in prose.

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 dense sentences with zero filler: capability and limit first, the getMessage substitution rule second, return shape and error behavior last. Every clause carries information an agent needs, and the most decision-relevant fact (batching instead of repeated calls) is 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 a 7-parameter tool with no output schema, explaining the return envelope and partial-failure behavior is exactly the right compensation. Remaining gaps are the saveAttachments write-to-disk consequence and when to prefer getMessage — useful but not fatal, since the schema describes each parameter fully.

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 coverage is 100%, so the schema already documents messages, rawSource, bodyFormat, headersOnly, rawEncoding, maxBodyChars and saveAttachments in detail. The description reinforces only the headersOnly threshold (10 vs 200) and otherwise defers to the schema; baseline 3 applies when the schema does the heavy lifting.

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 ("Read up to 10 messages in one call") plus the batching scope, and distinguishes itself from the sibling getMessage by saying output is "each as getMessage returns it" and that it replaces repeated getMessage calls. An agent can pick it over getMessage/getRecentMessages without opening any schema.

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?

Gives an explicit selection rule: use this instead of repeated getMessage calls, and switch to headersOnly when you need up to 200 messages rather than 10. It names the alternative (getMessage) but leaves the converse unsaid — nothing tells the agent to fall back to getMessage for a single message or when a full body beyond 10 items is needed.

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