Get one message

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds meaningful behavioral context beyond those annotations: the message is cached and returns the untruncated body, action buttons, and attachments. This gives the agent a fuller picture of what a successful call provides.

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 sentences, each earning its place: the first states the core operation and return details, the second tells the agent where valid IDs come from. There is no filler, repetition, or unnecessary explanation.

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 low-complexity read tool with an output schema, full schema parameter coverage, and safety annotations, the description is largely complete. It could mention error behavior or the cached nature's implications, but those are minor gaps given the available structured metadata.

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 the schema already documents both id and topic including the topic default. The description adds that IDs originate from list_messages or publish_message, which is helpful for sourcing the parameter but does not change the semantic meaning of either parameter.

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 opens with a specific verb and resource: 'Fetches a single cached message in full.' It adds what 'full' means—untruncated body, action buttons, and any attachment—so the agent knows exactly what this tool returns and can distinguish it from list_messages or get_account.

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 gives clear invocation context: it is for fetching one message by ID, and it explicitly says IDs come from list_messages or the result of publish_message. It does not explicitly state when not to use it, but the sibling names and this provenance guidance make the intended usage clear.

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