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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds genuine behavioral value beyond that by disclosing what the payload deliberately omits (API key, CSS, templates), which prevents false expectations about returned fields. It stops short of stating auth requirements.

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?

A single compact sentence plus the REST endpoint. The identifying qualifier ('by id') and the payload scope are front-loaded with zero filler.

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 partially compensates by naming what the response includes and excludes. For a one-parameter read-only fetch this is close to sufficient, though an explicit route-to-sibling note would complete it.

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% with a single UUID/prefixed-id parameter fully documented in the schema. The description's 'by id' adds no syntax or format detail beyond what the schema already provides, so the baseline 3 applies.

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+resource ('Get' a single newsletter by id) and scopes it further with 'settings and identity only; no API key, CSS or templates'. An agent can distinguish this retrieval-by-id tool from buttondown_list_newsletters without opening either 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?

Usage is implied by 'by id' — this is the single-record fetch. However, it never explicitly routes the agent away from alternatives (e.g. list_newsletters for enumeration, or update tools for mutation), so guidance is only inferred.

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