tslink

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Explain service access

access_explain

Read-onlyIdempotent

Explain a service's locally registered access: exposure, allow-list enforcement, and uncovered layers. Use it to answer who can reach it, without claiming live tailnet or backend auth facts.

Instructions

Explain what TSLink knows locally about one service's access: its exposure, whether an allow-list is enforced, and which layers this answer does not cover. Use this to answer "who can reach this?" honestly; it reads the local registry and proves nothing about live tailnet policy or backend authentication.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`service`	Yes	Exact registered service name.

Output Schema

TableJSON Schema

Name	Required	Description
`service`	Yes
`summary`	Yes
`tslink_known`	Yes	What the local registry records: service type, endpoint, exposure, tags, redacted allow-list, backend, and target loopback classification.
`schema_version`	Yes
`backend_auth_assumption`	Yes	Backend application, database and SSH authentication are outside TSLink and are not proven here.
`external_policy_unknown`	Yes	Layers this command does not evaluate: tailnet membership, ACL/grants, sharing, tag ownership, Funnel policy.
`tslink_local_enforcement`	Yes	Which TSLink HTTP enforcement applies, its failure mode, and whether public Funnel exposure is configured.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 19, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations cover the safety profile (readOnly, idempotent, openWorld=false), and the description adds substantive detail beyond them: the data source ('reads the local registry') and the honest limits of the answer (no live tailnet policy, no backend authentication). That is exactly the kind of scope disclosure annotations cannot carry.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, front-loaded with the tool's purpose, followed by usage and caveats. Tight overall, though the second sentence packs usage, semantics, and two caveats into one long clause.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Output schema exists so return values need no explanation. The description supplies data source, answer scope, and explicit non-coverage, which is everything an agent needs to call this correctly and interpret the result without overclaiming.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the single 'service' parameter is fully documented in the schema, so the description adds no syntax or format meaning beyond it. Baseline 3 applies when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (explain) and resource (one service's access) and enumerates exactly what the answer contains: exposure, allow-list enforcement, and uncovered layers. This is clearly distinguishable from sibling read tools like access_log or access_summary.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit usage context ('use this to answer "who can reach this?" honestly') and a boundary condition (it proves nothing about live tailnet policy or backend authentication). It stops short of naming a sibling alternative for when live-policy answers are needed, so it is clear context without full routing guidance.

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