get_emails_by_ids

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

Annotations declare readOnlyHint=true, and the description adds valuable behavioral context beyond that: it discloses the batch failure semantics ('One failed id does not fail the whole batch — check each result's ok field') and the 25-item limit. This goes beyond the annotation's safety profile.

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?

Four sentences, each with a clear purpose: what it does, when to use, failure behavior, and alternative. No filler or repetition. The description is front-loaded with the core purpose.

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?

Given the tool has no output schema and only readOnlyHint annotation, the description carries the burden of explaining the return envelope ('ok field'), usage context, and limitations. It covers use cases, exclusions, and error behavior, making it sufficient for an agent to select and invoke correctly.

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 descriptions cover 100% of parameters, so baseline is 3. The description adds meaning by clarifying that emailIds are 'composite' and come from prior search/email results, which is not in the schema. It also reinforces the max 25 constraint. However, it does not add detail for preferHtml or maxBodyLength beyond their schema descriptions.

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 ('Fetch') and resource ('full content for multiple emails by composite id'), clearly distinguishing it from siblings like get_email_by_id (single) and search tools (search vs fetch by id). The phrase 'in one call (max 25)' adds precise scope.

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?

Explicitly states when to use: 'Use to read a batch of specific messages from a prior get_emails/search_emails/search_indexed_emails result' and explicitly recommends an alternative: 'Prefer get_email_by_id for a single message.' This is clear, actionable guidance.

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