set_pin

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

With no annotations, the description carries the burden and largely does: it discloses that the write is a full in-place rewrite of one lane rather than a delta or append, which is the key destructive-behavior fact. It stops short of permission requirements or what happens to sibling lanes / an absent pin, so not a 5.

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?

Three dense sentences, front-loaded with the trigger and the object, each carrying distinct information (trigger, scope, semantics, sibling routing). No 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?

An output schema exists, so return values need not be explained, and the description covers trigger, scope, write semantics, and the memory-vs-state boundary. Minor gaps remain around overwrite edge cases (missing lane, other lanes' fate) that a mutation tool with no annotations could generously include.

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 0%, so the description must compensate, and it does: it reveals that 'channel' is one of work|personal|school (an enum the schema omits entirely) and that 'content' must be full state, not a delta. It adds real meaning beyond the bare 'string' schema, though it doesn't define channel format for content syntax.

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?

Specific verb+resource ('set the pin for ONE lane') with scope made explicit (single lane, enumerated values). It also distinguishes itself from write_memory, so an agent can route between a state pin and durable memory without opening either schema.

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?

States the trigger ('Session close') and the exclusion ('Durable facts belong in write_memory'), naming the alternative and the condition that selects it. This is exactly the when/when-not guidance that makes a writer tool selectable.

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