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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false, but the description adds genuine context beyond them: this is a two-phase request that requires the other party's approval before it takes effect. It also discloses a specific edge-case outcome (the response returns incoming_request and no acceptance occurs), which is real behavioral value not derivable from 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?

Front-loaded with the action verb and resource, and the routing caveat comes last. Mostly earns its sentences, though 'using the same rules as add_contact' is slightly opaque without consulting the sibling.

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?

An output schema exists, so return-value explanation is not required, yet the description still proactively explains the notable incoming_request response. For a mutation tool with annotation coverage and only two params, this is adequate, with the only real gap being match_id provenance.

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 50%: idempotency_key is documented in the schema, but match_id has no description. The description gestures at how the match is named ('by handle and by the name they saved') but does not explain where match_id comes from or its format. Baseline 3 is appropriate given the schema carries the idempotency semantics.

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: sends a contact request to an address book match. It distinguishes itself from siblings by reference ('same rules as add_contact') and routes the incoming_request case to respond_contact_request. An agent can tell it apart from add_contact, list_address_book_matches, and dismiss_address_book_match.

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 a clear prerequisite ('needs the person's OK first') and an explicit exclusion with alternative: if the person already asked the human, nothing is accepted and the human uses respond_contact_request. It does not, however, cover the full set of related siblings such as dismiss_address_book_match or when to prefer add_contact.

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