List email contacts

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

Annotations only declare readOnlyHint/openWorldHint, yet the description adds substantial behavior: a 50-item page cap, the exact field set with nothing else, exclusion of unsubscribed contacts, cursor/null end-of-list semantics, and a prompt-injection warning to treat contact names as data. That is far 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?

Front-loads 'Read only' and the resource scope, then packs consent semantics, field list, filters and pagination into a few dense but non-redundant sentences. Nothing repeats the schema verbatim and no sentence is 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 compensates by enumerating the exact returned fields, and it fully documents pagination and filtering behavior for a 6-parameter tool. An agent has everything needed to call it and interpret the response 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 coverage is 100%, so the baseline is 3, but the description adds real meaning: it explains what 'pending' consent actually represents, that the tag may be a name or id, that segmentId comes from postfjord_mail_overview, and that nextCursor must be passed back as cursor. Only the limit parameter is left entirely to the schema.

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 and resource ('list contacts') and immediately narrows the scope: only consenting contacts (confirmed, or pending with consent='pending'), never unsubscribed people. The enumeration of returned fields and the max-50 page size make it unmistakable versus siblings like postfjord_add_contact or postfjord_tag_contact.

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?

Gives clear usage context ('Use this to answer questions about the list, not to copy it elsewhere') and routes the agent to postfjord_mail_overview for segment ids. It lacks an explicit when-not-to-use statement relative to other list tools, but the intended call situation is unambiguous.

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