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

With no annotations, the description fully discloses side-effects: 'new TTL applies on the next GC tick (within 60s)', the ownership gate ('must own the channel — same gate as DELETE'), and the semantic effect ('Bumping rescues sessions... shrinking evicts idle sessions sooner'). This is model behavioral transparency, far beyond a basic 'updates TTL'.

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?

Every sentence earns its place: a clear purpose, two concrete use cases, required args summary, side-effect timing, behavioral consequences, and explicit exclusions. It is front-loaded and structured logically, with no redundancy or fluff.

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 3-param mutation tool with no annotations and no output schema, the description covers everything needed: what changes, when it applies, who is allowed, what it affects, and what it doesn't. The inclusion of the GC timing and ownership gate makes it fully self-contained.

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% for all 3 parameters, so baseline is 3. The description adds meaningful context, reinforcing that session_token is the creator's token and explains the TTL range semantics with '1 to 86400'. It doesn't add new syntax but strengthens understanding of ownership and effect, earning a 4.

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 opens with a specific verb+resource+scope: 'Bump (or shrink) the idle session TTL on an existing channel'. It immediately distinguishes from siblings like create_channel by stating 'without recreating it', making it clear this is an in-place mutation.

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?

Explicit when-to-use scenarios are provided: 'when an agent started a short-TTL channel... conversation extended past the original window' and 'when sessions are getting GC'd before peers come back'. It also clarifies what it does NOT do ('Does NOT touch trust_mode... only the TTL field'), setting expectations for alternatives.

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