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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds valuable context beyond that: no credits are deducted, it reads only from saved Xmagnet contacts, returns up to 50 contacts with empty params, and includes enriched fields. This gives a clear picture of cost, scope, and behavior without contradicting annotations.

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?

The description is three sentences, front-loaded with the most critical directive ('ALWAYS call this tool immediately'). Every sentence adds value: purpose, usage guidance, and key behavioral details. No fluff or redundancy.

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's complexity (13 params, no output schema), the description covers the essentials: core use case, default behavior, credit implications, and what data is included. It could be more complete by mentioning pagination details or filter combination, but the strong annotations and clear usage guidance make it sufficient for most cases.

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 only 23%, so the description should compensate for undocumented parameters. It does add useful high-level guidance (empty params returns all contacts), and the parameter names (city, company, skills) are self-explanatory. However, it doesn't explain filter behavior or relationships between parameters, leaving room for ambiguity with 13 parameters.

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 clearly states the tool searches contacts saved in Xmagnet, with a specific verb ('Search') and resource ('contacts'). It explicitly differentiates from siblings by noting 'reads from saved Xmagnet contacts only' and 'No credits deducted', making it distinct from external search tools like search_contacts or find_contacts_at_companies.

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 description gives explicit when-to-use guidance: 'ALWAYS call this tool immediately when the user asks to show, list, or retrieve their contacts/people.' It also advises calling with empty parameters to return all contacts. However, it doesn't explicitly mention when not to use it or alternatives, so it falls short of a full 5 by the rubric.

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