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

Annotations provide only a title, so the description carries the full behavioral burden. It does disclose that this is a read operation and that only caller-owned messages are accessible, which is useful auth context. Yet it stops there, with no mention of what the response contains, error behavior, or any further side-effect characteristics.

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?

The description is a single efficient sentence: 'Read one stored message owned by the caller, by id.' It front-loads the action and object, includes the ownership boundary, and contains no filler or repetition.

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 simple one-parameter read tool with no output schema, the description covers what the tool does, the ownership scope, and how the message is identified. It is slightly thin on return-value detail thoracic behavior, but for this simple tool the core context is present.

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%: the only parameter, id, is already described as 'Stored message id' in the schema. The description essentially repeats 'by id' without adding format, constraints, or usage nuances, so it adds no meaningful meaning beyond the structured input 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?

The description uses a specific verb ('Read'), a precise resource ('one stored message'), and the access path ('by id'), while also scoping ownership to the caller. This clearly distinguishes it from plural/list siblings like sms_sources and sms_history without needing to inspect the 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?

The description implies the right context: use this when you have a single stored message id and want that message. However, it never explicitly names alternatives or says when not to use it, such as 'use sms_sources to list messages instead,' so usage guidance remains implicit rather than explicit.

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