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 without description help. The description adds the useful fact that the response includes the full body and an analytics summary, but says nothing about auth needs, rate limits, or whether the body is HTML vs plain text.

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 compact fragments with the payload contents front-loaded and zero filler. The trailing "GET /emails/{id}" restates what the name and schema already convey, which is mildly redundant but not harmful.

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 sensibly compensates by enumerating the returned fields, which is the main thing an agent needs for a simple read. The remaining gap - response format details - is minor for a one-parameter, read-only fetch tool.

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% on a single required parameter, so the schema already explains the UUID/prefixed-id format. The description's "by id" merely confirms the role without adding format or constraint detail, which lands at the baseline 3.

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?

Names a specific verb and resource ("One email by id") and enumerates the payload returned (body, subject, status, publish date, slug, archive settings, analytics summary). It is clearly distinguishable from list_emails, though it never explicitly contrasts with get_email_analytics even though it overlaps that sibling's territory.

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 only implied by "by id" - the agent can infer this is the single-record fetch when the id is known. There is no explicit when-to-use statement, no guidance versus get_email_analytics or list_emails, and no prerequisites or exclusions.

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