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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful behavioral content by promising 'the campaign's full state' and listing the fields returned, but says nothing about failure behavior (unknown id), permissions, or rate limits, so it adds only moderate value beyond the structured fields.

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 short, front-loaded sentences that lead with the verb and resource and then the return payload. The trailing 'EmailOctopus: GET /campaigns/{campaign_id}' line is mildly redundant with the name and schema but harmless and short.

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?

There is no output schema, so the description usefully compensates by enumerating the returned fields, and for a one-parameter read tool the remaining needs are minimal. It loses a point only because error/edge behavior for an unknown campaign_id is unaddressed.

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?

With a single parameter and 100% schema description coverage, the schema already documents campaign_id fully. The phrase 'by its id' restates the schema rather than adding format, example, or sourcing guidance, 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 campaign by its id') and even enumerates the returned state (name, status, subject, from, content, created_at), which separates it from report-style siblings. It does not, however, explicitly name the sibling it differs from (e.g. emailoctopus_list_campaigns or get_campaign_report), so differentiation is inferred rather than stated.

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 purpose implies the usage context (fetch one existing campaign when its id is known), but there is no explicit when-to-use, when-not-to-use, or alternative routing (list_campaigns for enumeration, get_campaign_report for metrics). Minimum viable but with a clear gap.

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