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

Annotations already declare the operation is a non-destructive, idempotent write (readOnlyHint=false, destructiveHint=false, idempotentHint=true). The description adds that the effect mirrors the note's pin on the contact card and reinforces retry semantics, but does not say what happens if the note is already pinned, whether the previous state is returned, or what errors look like.

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 core action and the true/false mapping are front-loaded in a single clause, and the two follow-on sentences are short and purposeful. The phrase 'as the note's pin on the contact card does' is slightly circular and adds little.

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?

For a four-required-parameter mutation with no output schema, the description covers purpose, the boolean's semantics, id argument provenance, and retry behavior. It stops short of stating error/edge-case behavior or permission requirements, which keeps it from being fully complete.

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 only 25% (only idempotency_key is documented), so the description must carry weight. It does: 'pinned: true/false' explains the boolean's meaning, noteId's origin is tied to the read tool, and retry reuse of idempotency_key is restated. Only client_id is left unaddressed, which is largely self-evident.

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 names a specific verb+resource ('Pins a note to the top of a contact's card') and even disambiguates the direction via '(pinned: true) or unpins it (false)'. It is clearly distinct from add_client_note and delete_client_note by action, though it never names a sibling explicitly.

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?

It gives a real sourcing hint ('noteId comes from read (entity client notes)') and a retry rule for idempotency_key, which is useful operational guidance. However, there is no explicit when-to-use vs when-not framing, and no statement about prerequisites such as permissions or whether the note must already exist.

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